Personal rivalries are rare in today's NBA, but it's possible one of the league's best could be coming to a close Wednesday night.

The second and final game of the year between the Brooklyn Nets and San Antonio Spurs could be the last one ever to pit Tim Duncan and Kevin Garnett head-to-head, with rumors already swirling that either could retire at the end of this season.

For all we know, the final contest between the two future Hall of Famers already happened back on Nov. 22, when the Spurs defeated the Nets 99-87. Garnett doesn't tend to play on the end of back-to-backs, and after running 29 minutes during Tuesday evening's 98-93 victory over the New York Knicks, the Duncan-Garnett rivalry could already be over without us even knowing it. 

"Obviously, two of the all-time greats in our sport," Garnett's teammate, Jarrett Jack, says about the upcoming matchup. "That'll be something. Those guys have had countless battles over the years and definitely one that I don't think any of us are ready to see end."

So, if this really is the end, what is the NBA to do without two of its all-time big men, a couple of the 15 best all-time players—if not better than that? 

After six combined rings (and maybe more with the defending-champion Spurs sitting at 13-4), Duncan and KG are the purest examples of how success can be built upon different personalities. 

Duncan is unheard. He's left no trail of existence—from Saint Dunstan's Episcopal to Wake Forest to San Antonio to (probably) the Milford School—outside of what's on the back of his basketball card. He's an introverted superstar who has somehow managed to avoid commercials, scandal, bad press and fan backlash during an era in which that seems somewhat impossible.

Garnett, meanwhile, doesn't even need a cell phone, because you can hear him from across the world.

Need proof of their contrasting personalities? Just go to today's form of a library: YouTube. Search Duncan, and you'll find this recent Foot Locker commercial, an example of him jousting at his own relaxed persona:

Now, compare Duncan's plant attack to Garnett's assault on Rajon Rondo's ears during 2010 Boston Celtics media day:

Introverted vs. extra crazy. It's the only way to describe it. But a combined 29 All-Star Games (15 for Garnett, 14 for Duncan) and three MVPs later, they've tried to teach us that there isn't a singular correct way to win in the NBA.

The above is a concept sports fans struggle with consistently. Public perception often says that if a player doesn't have Michael Jordan's or Kobe Bryant's personality, it means he doesn't have his drive. We heard those critiques about LeBron James. About Peyton Manning. We'll hear them about more athletes in the future.

Duncan, though, always had the fortune of winning in the most business-like manner possible, and we immediately thrust the "winner" label upon him, similarly to how baseball fans have treated Derek Jeter since he helped the Yankees win the 1996 World Series during his rookie season. And Duncan deserves that moniker as much as anyone. 

One of the best stats in sports is that Duncan's Spurs have won at least 50 games in 16 of his 17 complete NBA seasons. The one time they didn't? The strike-shortened 1998-99 season, when the entire year was only 50 games long, and all the Spurs did was go 37-13 on the way to garnering their first of five championships with Timmy and Gregg Popovich.  

KG went another direction, struggling to win in the playoffs for all those years in Minnesota until finally making it to the 2004 Western Conference Finals with some help from Sam Cassell and Latrell Sprewell. 

"Those are two of the greatest power forwards to ever play," says second-year up-and-comer Mason Plumlee, who watched Duncan and Garnett growing up and is now teammates with KG in Brooklyn. "Obviously, they're at a different point in their careers now, but to us, [it's] kind of a special, individual rivalry."

No matter how they got there, we're talking about two of the best power forwards of all time. The only way to argue against that is to claim Duncan isn't actually a power forward, a completely legitimate—if not correct—point. But competitiveness has a funny way of showing up, regardless of how different two people's superficial personalities may seem.

Take two men who would likely turn a Saturday afternoon stroll through the park into some kind of competition, throw them in a superior Western Conference, let them compete for MVPs, duke it out in the playoffs and fight for titles, and you probably won't find friendliness on the other end of the experiment.  

Duncan and Garnett aren't exactly best buds, at least according to Chris Ballard's excellent Sports Illustrated profile (via SLAM) on Duncan from May of 2012 (h/t to Eric Freeman of Yahoo Sports):

In fact, Duncan hates Kevin Garnett. Hates him the way liberals hate Sean Hannity. This information comes from very reliable sources, who talk about how KG has made a career of trying to punk Duncan, baiting him and slapping him and whispering really weird smack into his ear. They talk about how funny this is, because the worst thing you can do as an opponent is piss off Duncan. Then, as Malik Rose says, "he f------ destroys you." Duncan's lifetime numbers versus Garnett's teams, by the way: [19.4 points per game, 12.1 boards and a 32-19 record, including the postseason, as of Dec. 3, 2014].

Duncan is diplomatic about the topic. Asked if perhaps all those years battling Garnett have softened his feelings for the man, led to a Magic-Larry type of kinship, Duncan leans back on the couch in his hotel room and grins. There is a pause. A longer pause. Finally he says, "Define kinship."

Since this was written, Duncan is 3-0 in games he's played against Garnett's teams, piling on the wins one by one. It's stories like this that make it feel like the two Western Conference greats have an extensive playoff history, but that's not necessarily the case.

Duncan and Garnett have met only two times in the postseason: 1999 and 2001, when the Spurs rolled over the Minnesota Timberwolves in a couple of 3-1 first-round series. We always think of one-on-one rivalries developing in the playoffs (see: Paul Pierce and LeBron James) but Duncan and KG—that was just about basketball.

Maybe we would've seen more Duncan-Garnett postseason matchups if KG had more help. Even during that '04 Western Conference Finals run, the player who finished fourth on the Wolves in minutes per game was Trenton Hassell. He never had the help to make it to the top of the West, even when he almost got there anyway.

Clearly, Duncan isn't the only player with such strong feelings about Garnett. We did, after all, just have Bitegate (more clever name pending) less than a week ago when KG tried to clamp down on Joakim Noah's hand between plays.

"Yo, man, he tried to bite me, man," Noah, who has a history with Garnett, said after Sunday's Nets-Bulls game, via Tim Bontemps of the New York Post. "That’s crazy man. I mean, it's unbelievable."

But that's KG—the ultimate instigator.

Duncan, though, wouldn't even knock over the plant, and it's not that he's too nice of a guy to do it. It's that we really don't know what kind of a person he is, at all. He's as closely guarded as the opposing big men he mans on a nightly basis.

There is an all-time (or horrifying, depending on your point of view) quote from Early Wynn, the MLB Hall of Fame pitcher from the '40s and '50s who was known for his intensity and propensity to throw at batters.

"I'd knock down my own grandmother if she dug in on me."

Wynn was somewhat the KG of his time. He was a tough, feisty, win-at-all-costs athlete who played in a period when intensity had a different meaning. There weren't hold-me-back moments back then. If a pitcher threw high and in, he didn't have umpires, security guards, public perception or a DH to help him, and he'd likely have to deal with the repercussions later.

Some, like ESPN's Jalen Rose, may diagnose Garnett with a slightly different, more modernized mindset, labeling him as one of those aforementioned hold-me-back guys. But he's still the instigator, the one who causes the ruckus. And their joint legacy is that Duncan is the one who will never react to it. 

Fred Katz averaged almost one point per game in fifth grade but maintains that his per-36-minute numbers were astonishing. Find more of his work at WashingtonPost.com or on ESPN's TrueHoop Network at ClipperBlog.com. Follow him on Twitter at @FredKatz.

Quotes obtained firsthand, unless stated otherwise. Unless otherwise noted, all statistics are current as of Dec. 3 and are courtesy of Basketball-Reference and NBA.com.