Who says we only need to have a single NBA GOAT?

That designation typically comes down to a battle between Michael Jordan and LeBron James, but let's throw those two legends of the sport into different categories—shooting guards and small forwards, respectively.

Even though the league is moving further from traditional positions every year, they're still handy-dandy guides and will remain such so long as starting lineups contain five distinct spots. Sure, some players are combo guards, swingmen or tweener forwards. Power forwards and centers can often be interchangeable, and not everyone fits cleanly into one of the overarching choices. 

But we can still sort everyone into positional boxes—some cleaner than others—and then determine the GOAT from each one. 

We're concerned with anything and everything that happened on the court. Peak performances matter. So too does longevity, as well as objective looks at the entirety of a career and the subjective legacy elements that color our impressions of a player. If it has to do with on-court production, it's relevant for our purposes.

Journey with us as we run from point guard to center, looking at the all-time GOAT at each position. We'll also delve into the next tier of candidates and the most notable current challenger for that featured spot, some of whom are more realistic threats than others. 

Point Guard: Magic Johnson

Years Played: 1980-96

Teams: Los Angeles Lakers

Career Per-Game Stats: 19.5 points, 7.2 rebounds, 11.2 assists, 1.9 steals, 0.4 blocks

Career Advanced Metrics: 24.1 PER, 61.0 TS%, 155.8 WS, 0.225 WS/48, 6,179.54 TPA

What might have happened if Magic Johnson didn't need to hang up his sneakers due to HIV after the 1990-91 season? 

That was only his age-31 campaign, and he averaged 19.4 points, 12.5 assists and 7.0 rebounds while shooting 47.7 percent from the field and making 90.6 percent of his free-throw attempts. Based on basically every common-use advanced metric, he was playing above his lifetime level, showing few signs of imminent decline as he moved deeper into his 30s. 

Johnson cemented an indelible legacy even before that point, leading the Showtime Los Angeles Lakers to a decade of unabashed dominance while he established himself as a wizard of a passer who played with immense effectiveness and flair. He was a show unto himself, even on the rare off nights in which he struggled to score and find passing lanes against defenses that compressed back into the paint. 

As one example among myriad displays of excellence, Johnson is one of only six players to record at least 22 points and 11 assists per game during a qualified season. He and fellow Hall of Famer Oscar Robertson (three apiece) are the lone players to record multiple such campaigns. 

But again: What if he hadn't needed to take a four-year hiatus before returning for 32 games in 1995-96? 

He already sits at No. 10 in lifetime TPA earned during the regular season, and merely replicating his worst effort from the four healthy efforts prior to his pseudo-retirement (288.53 TPA in 1987-88) for three more go-rounds would've pushed him to No. 5. That would have been nine spots ahead of Chris Paul and all other point guards in the sport's history.  

Next Up: Chris Paul, Oscar Robertson, John Stockton, Jerry West

Biggest Current Challenger: Stephen Curry

Paul is closer to surpassing Johnson than many might think, although the lack of jewelry (both of the team and individual varieties) could make the necessary legacy gains an impossibility. Stephen Curry, however, suffers from no such limitations after already earning two MVP awards and a trio of titles. 

The point guard is already one of the 50 best players in the sport's history, but he has a long way to go before matching Johnson. He still sits behind 34 others in lifetime TPA and is 93rd in career win shares (Johnson is 21st).

Nonetheless, he's the top current challenger because of his enduring level of play, relative youth and potential knack for staving off Father Time. Given his deadly shooting stroke, Curry should age far more gracefully than the many floor generals dependent on physicality to generate their production. 

Shooting Guard: Michael Jordan

Years Played: 1985-2003

Teams: Chicago Bulls, Washington Wizards

Career Per-Game Stats: 30.1 points, 6.2 rebounds, 5.3 assists, 2.3 steals, 0.8 blocks

Career Advanced Metrics: 27.9 PER, 56.9 TS%, 214.0 WS, 0.25 WS/48, 7,924.63 TPA

Could this be any more obvious?

Regardless of your stance in the Michael Jordan vs. LeBron James debate that seems to take new life at every twist and turn of the NBA calendar, you should recognize the former's supremacy at shooting guard. Despite what the diehard Kobe Bryant supporters might believe, no other backcourt player has come close to Jordan's lengthy resume. 

Just take a gander at the top seasons by 2-guards in NBA history, based on NBA Math's GOAT project, wherein GOAT points are determined by excellence relative to the rest of the league during any given campaign:

1. 1988-89 Michael Jordan
2. 1987-88 Michael Jordan
3. 2017-18 James Harden
4. 1990-91 Michael Jordan
5. 1990-91 Michael Jordan
6. 1992-93 Michael Jordan

That's rather telling. And it's perhaps even more telling that Jordan alone has six of the top 10 seasons by 2-guards, as well as 10 of the top 20. Suffice it to say, he's in a class of his own.

He wreaked havoc for the Bulls throughout his extended prime by routinely making All-Defensive teams and submitting some of the greatest scoring numbers in NBA history. 

You've heard about his six-for-six record in the Finals. You know about the MVPs and scoring titles. You've watched the famous moments—the ones at the expense of Bryon Russell, Craig Ehlo and so many others. Convention is convention for a reason here. 

Next Up: Kobe Bryant, Clyde Drexler, Allen Iverson, Dwyane Wade

Biggest Current Challenger: James Harden

With Bryant retired, Dwyane Wade still deciding if he wants to return for another season and Donovan Mitchell far too young to battle for the top spot at his position, James Harden is the easy choice as the primary challenger to Jordan.

However, he isn't going to match Jordan's legacy. Sorry, but that's the truth. 

Harden is an offensive genius who's breaking new ground with his combination of point-producing volume and free-throw-driven efficiency, but his defensive woes and relatively delayed breakout leave him far behind the positional leader. Perhaps he'll eventually supplant Allen Iverson for the final spot within the 2-guard top five. He could even climb into the tier that includes Wade and Drexler.

Either way, his ceiling is still capped well shy of Jordan's. 

Small Forward: LeBron James

Years Played: 2004-present

Teams: Cleveland Cavaliers, Miami Heat, Los Angeles Lakers

Career Per-Game Stats: 27.7 points, 7.4 rebounds, 7.2 assists, 1.6 steals, 0.8 blocks

Career Advanced Metrics: 27.7 PER, 58.6 TS%, 219.4 WS, 0.238 WS/48, 9,831.01 TPA

Talented as Larry Bird may have been—and his playing style, complete with defensive switchability and perimeter-shooting acumen out of the frontcourt, would've fit even better in the present day than the '80s—LeBron James has moved past him with room to spare.

We can compare a host of advanced metrics to see how James proves Bird's superior in both efficiency and volume:

• PER: 27.7 for James, 23.5 for Bird
• TS%: 58.6 for James, 56.4 for Bird
• WS: 219.4 for James, 145.8 for Bird
• WS/48: 0.238 for James, 0.203 for Bird
• TPA: 9,831.01 for James, 6,119.77 for Bird

That's a clean sweep. 

Back in April 2015, I placed James at No. 7 and Bird at No. 9 in my Legends 100 rankings, which looked at the entirety of careers rather than just peak levels. Since then, the man who's made eight consecutive Finals appearances has averaged 26.4 points, 8.2 rebounds and 8.2 assists while slashing 53.7/35.0/71.2, and he played at perhaps his highest level ever while willing the Cleveland Cavaliers through the Eastern Conference in the 2018 postseason. 

He's only widened the gap between himself and every other small forward in NBA history. And the chasm isn't done growing yet, as FiveThirtyEight's CARMELO forecast indicates his expected level of play will be worth $86.6 million in the coming season before falling to $74.4 and $70 million in 2019-20 and 2020-21, respectively. 

Next Up: Elgin Baylor*, Larry Bird, Kevin Durant, John Havlicek

*Note: Julius Erving replaces Elgin Baylor if we include ABA achievements. 

Biggest Current Challenger: Kevin Durant

Kevin Durant is a historic, transcendent player who's only gotten better since he joined the Golden State Warriors—a choice that led to a pair of titles and an equivalent number of Finals MVPs. If he doesn't beat you with his legendary scoring chops, he can take over a game with his versatile defensive ability or growing status as a dangerous facilitator.

But his scoring prowess stands out the most. 

Throughout his career, Durant has averaged 27.1 points while shooting 49.0 percent from the field, 38.4 percent from downtown and 88.2 percent from the stripe. Among every player in history with at least 100 career appearances, that gives him the fifth-highest scoring average, behind only Wilt Chamberlain (30.1), Jordan (30.1), Baylor (27.4) and James (27.2). Better yet, he's the lone player with a true shooting percentage over 60 until we get down to No. 16 Adrian Dantley (24.3 points per game with a 61.7 true shooting percentage), No. 22 Stephen Curry (23.1; 62.1) and No. 25 James Harden (23.0; 60.8). 

Yet even with what might be the greatest scoring resume in the sport's history, Durant still isn't going to pass James. He's already the third-best small forward we've ever seen, behind James and Bird, but the remaining climb is far too steep when his contemporary rival is playing at an even higher level and had a massive head start.

Power Forward: Tim Duncan

Years Played: 1998-2016

Teams: San Antonio Spurs

Career Per-Game Stats: 19.0 points, 10.8 rebounds, 3.0 assists, 0.7 steals, 2.2 blocks

Career Advanced Metrics: 24.2 PER, 55.1 TS%, 206.4 WS, 0.209 WS/48, 5,908.75 TPA

In 2003-04, Kevin Garnett had the most impressive season we've ever seen from a power forward. You can make convincing arguments that Charles Barkley, Karl Malone, Dirk Nowitzki and perhaps even Bob Pettit had peaks at least comparable to Tim Duncan's best years. But the San Antonio Spurs mainstay elongated that peak throughout what was basically his entire post-Wake Forest basketball career, to the point that his early efforts and post-prime endeavors are almost indistinguishable in terms of value added. 

During his rookie season in 1997-98, Duncan averaged 21.1 points, 11.9 rebounds, 2.7 assists, 0.7 steals and 2.5 blocks while shooting 54.9 percent from the field. He earned 0.192 win shares per 48 minutes. Seventeen years later, Duncan posted 13.9 points, 9.1 rebounds, 3.0 assists, 0.8 steals and 2.0 blocks per game while shooting 51.2 percent from the field during his age-38 season. He didn't spend as much time on the court and focused more on defense than offense, but he still produced a whopping 0.207 win shares per 48 minutes.

That longevity is what pushes him ahead of everyone else at the position. 

It remains a travesty that one of the greatest defensive presences in league history never held up the Defensive Player of the Year trophy, but that doesn't hold back Duncan's resume. He was still a consummate professional who excelled in nearly every facet of the game and turned the Spurs into a dynasty. Without him, San Antonio wouldn't have enjoyed a 21-year streak of postseason appearances, earned a handful of titles and become the ultimate model of consistency in professional basketball.  

Next Up: Charles Barkley, Kevin Garnett, Karl Malone, Dirk Nowitzki

Biggest Current Challenger: Anthony Davis

Predicting that someone will eventually dethrone Duncan is foolish, if only because that requires so many fortuitous bounces and luck with injuries. A player can't only ascend to the top of the individual hierarchy; he must also sustain that level—or at least a comparable one—for nearly two decades. 

That's troubling for an up-and-comer like Anthony Davis, who has played remarkably well when healthy but has already struggled with some maladies during the early stages of his career. Even if he continues getting better and eventually leads the New Orleans Pelicans to the promised land, are we going to feel comfortable betting on him remaining near the top of the pack until 2030?

Even if Davis kept replicating the 316.46 TPA he earned during the 2017-18 regular season and playoffs combined, he'd need another 15 seasons to move past Duncan's career tally. In other words, he'd have to play at the exact same level through the 2032-33 campaign—his age-39 season. 

And yet, he's still the best choice here, since the other leading options at the 4 include players without lofty enough peaks (LaMarcus Aldridge, Draymond Green, Blake Griffin, Kevin Love) or lengthy enough resumes (Kristaps Porzingis, Lauri Markkanen, Jayson Tatum) to reasonably factor into the conversation.

Center: Kareem Abdul-Jabbar

Years Played: 1970-89

Teams: Milwaukee Bucks, Los Angeles Lakers

Career Per-Game Stats: 24.6 points, 11.2 rebounds, 3.6 assists, 0.9 steals, 2.6 blocks

Career Advanced Metrics: 24.6 PER, 59.2 TS%, 273.4 WS, 0.228 WS/48, 9,067.57 TPA

Kareem Abdul-Jabbar was never better than he was during his early-career years with the Milwaukee Bucks. He spent only six seasons in Brewtown before "cultural differences" sparked his exit via trade to the Los Angeles Lakers, but he racked up three MVPs and a championship while averaging 30.4 points on 54.7 percent shooting, 15.3 rebounds and 4.3 assists. 

The master of the skyhook had to take a slight backseat to Magic Johnson during portions of his Lakers tenure, but he still played excellent basketball for an even longer duration while compiling three more MVPs and another five titles. Either resume would leave him rather high on the career TPA leaderboard. In fact, take a gander at his placement among the best centers the sport has ever offered: 

1. Wilt Chamberlain: 8.318.34 TPA
2. Bill Russell: 5,897.53 TPA
3. David Robinson: 5,406.22 TPA (Robinson should be included in the "next up" section, but he was a difficult cut as we strove to cull that list to four players.)
4. Hakeem Olajuwon: 5,167.04 TPA
5. Los Angeles Lakers Kareem Abdul-Jabbar: 5,038.31 TPA
6. Shaquille O'Neal: 4,860.12 TPA
7. Milwaukee Bucks Kareem Abdul-Jabbar: 4,029.26 TPA
8. Wes Unseld: 3,273.37 TPA
9. Pau Gasol: 3,150.84 TPA
10. Bob Lanier: 3,002.73 TPA

Stop and think about that. Only four men have exceeded Abdul-Jabbar's Lakers-era tally during their entire careers. Five have topped his efforts for the Bucks. And we're talking about both in conjunction, which is why only Bill Russell and Wilt Chamberlain deserve to sit within a single tier of the GOAT center—a man who deserves more love in the overall GOAT conversation. 

Maybe Chamberlain was better during his peak years, scoring points in bunches and flashing the passing skills necessary to lead the league in total assists during the 1967-68 season. Perhaps Russell's legacy is comparable with so many titles earned for the Boston Celtics. But the remarkable longevity and sustained excellence pushes Abdul-Jabbar beyond both of them. 

Next Up: Wilt Chamberlain, Hakeem Olajuwon, Shaquille O'Neal, Bill Russell

Biggest Current Challenger: Rudy Gobert

If you'd like to name Joel Embiid, Nikola Jokic or Karl-Anthony Towns here, that's your prerogative. They're all justifiable choices. You could even argue none have demonstrated enough to belong in the same sentence as Abdul-Jabbar and instead select Deandre Ayton for his lofty potential and currently flawless resume. After all, a player can't have done anything wrong when he's the reigning No. 1 pick who has yet to play in the Association.

Ultimately, all fall short. This section only exists for the sake of completeness, since no center in the current NBA looks likely to challenge the legends of yesteryears as the game increasingly distances itself from its post-up orientation. 

Gobert is our choice here because of his consistent excellence when healthy. He's a game-changing defensive force for the Utah Jazz, and he's coming off a season in which his team was 6.9 points per 100 possessions better with him on the floor. When he plays, the opposition has no choice but to alter its offensive schemes.

Gobert isn't going to become the greatest center in NBA history. But the established nature of his play, expectations of health and relative youth push him into the forefront for the current crop. 

Adam Fromal covers the NBA for Bleacher Report. Follow him on Twitter: @fromal09.

Unless otherwise indicated, all stats courtesy of Basketball Reference, NBA.com, NBA Math or ESPN.com.