Not all MLB contenders are built for postseason success.

From the makeup of the starting rotation to the depth of the bullpen to the reliability of the offensive attack, a team needs to check all the boxes to go on a World Series run.

With the 2021 regular season winding to a close and the start of the playoffs right around the corner, the postseason landscape is still taking shape.

Entering play Thursday, 16 teams had at least a glimmer of a chance of earning a playoff berth, according to the odds from FanGraphs.

Ahead, we'll take a closer look at each of those clubs and buy or sell them as legitimate World Series contenders, based on how their roster profiles for success in the bright lights of October.

Fleeting Playoff Hopes

Cincinnati Reds (3.2 percent chance)

The Reds are 7-15 in their last 22 contests, and the offense has sputtered along with a .712 OPS and 3.9 runs per game during September. The trio of Luis Castillo, Wade Miley and Tyler Mahle could be formidable in October, but first they need to get there, and that looks like a tall order they way they have played of late.

Buy or Sell: Sell

Seattle Mariners (2.1 percent chance)

The late-inning trio of Diego Castillo, Paul Sewald and Drew Steckenrider could shorten a lot of games for the Mariners in the postseason, but a mediocre starting rotation that ranks 19th in the majors with a 4.55 ERA could pose a problem. This is a team on the rise, but the M's are still a few years away from legitimate contention, even if they sneak into the playoffs.

Buy or Sell: Sell

Oakland Athletics (0.5 percent chance)

The Athletics have scored three or fewer runs in five straight games, including three straight losses to a Mariners team they are battling for wild-card position. The return of Chris Bassitt (facial fractures) should be a major shot in the arm for the rotation, and the duo of Matt Olson and Starling Marte continue to carry the offense. However, they've gone an ugly 28-47 against teams with a winning record, making it hard to view them as title contenders.

Buy or Sell: Sell

San Diego Padres (0.2 percent chance)

Since Aug. 10, the Padres have the worst record in the National League and the second-worst record in baseball at 10-26 with a minus-65 run differential. The roster is loaded with high-profile talent, but it's hard to envision them pulling out of this tailspin in time to make the playoffs.

Buy or Sell: Sell

Philadelphia Phillies

Playoff Chances: 16.5 percent

With a 6-2 record in their last eight games, the Philadelphia Phillies are making a strong late push behind NL MVP front-runner Bryce Harper and NL Cy Young candidate Zack Wheeler.

Harper is hitting .358/.488/.776 with seven home runs and 17 RBI in 20 games this month, while Wheeler has gone 3-0 with a 1.14 ERA, 0.97 WHIP and 32 strikeouts in 23.2 innings over four starts.

However, the rest of the rotation is not pulling its weight.

Left-hander Ranger Suarez has been a huge addition to the rotation after starting the year in the bullpen, but veterans Aaron Nola (4 GS, 5.85 ERA) and Kyle Gibson (4 GS, 7.48 ERA) have both struggled in September, and the relief corps continues to be shaky at best.

They still have three games left against the NL East-leading Atlanta Braves, along with series against the Pittsburgh Pirates and Miami Marlins, so they could sneak into the playoffs.

It's hard to trust their pitching staff to lead them on a deep run.

Buy or Sell: Sell

New York Yankees

Playoff Chances: 49.0 percent

The road ahead is not an easy one for the New York Yankees as they chase a wild-card berth.

Their remaining series are against a trio of AL East contenders in the Boston Red Sox, Toronto Blue Jays and Tampa Bay Rays, and they've gone a combined 19-29 against those three teams.

It's been a roller coaster of a season for the Yankees, and the perfect embodiment of that came just a few weeks ago when they followed a 13-game winning streak with an ugly 2-11 stretch. However, the talent is there for this team to rip off another hot streak if it can punch its ticket to October.

Gerrit Cole is a bona fide ace, Nestor Cortes Jr. and Jordan Montgomery have been solid middle-of-the-rotation options, and Luis Severino could be a major X-factor as an opener or a multi-inning weapon after returning to action earlier this week following Feb. 2020 Tommy John surgery.

Fresh off a sweep of the Texas Rangers, this team has momentum for an important stretch run. If the Yankees can secure their spot, they are as dangerous as any American League club and can catch fire when it matters most.

Buy or Sell: Buy

Toronto Blue Jays

Playoff Chances: 52.0 percent

The Toronto Blue Jays can pile up runs.

Vladimir Guerrero Jr. has top-five numbers in the Triple Crown categories, Marcus Semien has launched 41 home runs, Teoscar Hernandez leads the team with 109 RBI, and Bo Bichette, Randal Grichuk and Lourdes Gurriel Jr. have joined that trio in slugging 20 home runs for a club that leads the majors with 241 long balls.

But it's the pitching staff that will determine Toronto's October shelf life.

Left-hander Robbie Ray has assembled an unlikely AL Cy Young run, and he'll likely be joined by Steven Matz, rookie Alek Manoah and deadline pickup Jose Berrios in the postseason rotation. That group has a chance to be great, but it's short on playoff experience and has had some ups and downs aside from Ray.

After going out with a whimper against the Tampa Bay Rays in the Wild Card Series last year, losing 2-0, this group has gained valuable experience and is as hot as any team in baseball. The Jays are young, and the rotation doesn't have any true marquee names, but the offense is good enough to mount a run similar to what the 2018 Boston Red Sox did.

If they can sneak into the postseason, look out.

Buy or Sell: Buy

Atlanta Braves

Playoff Chances: 85.6 percent

The Atlanta Braves were 44-44 when Ronald Acuna Jr. suffered a season-ending torn ACL on July 10, and it was easy to think that might end their chances of claiming a fourth straight NL East title.

Instead, the injury seemingly galvanized this team.

A breakout performance from Austin Riley and a handful of deadline additions have stabilized the offensive attack, while Max Fried and Charlie Morton are pitching like co-aces atop a young starting rotation that could be a strength in October.

A middling 29-38 mark against teams with a winning record and a 23-29 record in one-run games raises some questions about the Braves' ability to grind it out in the playoffs. The bullpen has been a big part of their close-game mediocrity, with a 4.05 ERA and 25 blown saves in 60 chances on the year, including six in 10 opportunities in September.

A likely opening-round battle of pitching staffs with the Milwaukee Brewers would leave them as heavy underdogs to begin their playoff run.

Buy or Sell: Sell

St. Louis Cardinals

Playoff Chances: 94.4 percent

The St. Louis Cardinals have gone from two games above .500 to a 4.5-game cushion for the second NL wild-card spot while ripping off an 11-game winning streak entering play Thursday.

Starting pitcher Adam Wainwright, 40, has found the Fountain of Youth, Jon Lester has quietly rounded into form after joining the rotation in a deadline deal, and young ace Jack Flaherty is set to return from a strained shoulder that has sidelined him since late August.

Genesis Cabrera, Alex Reyes and Giovanny Gallegos form the type of relief trio a team can lean on heavily in October, and with four starters over age 33, the rotation isn't likely to wilt under the bright lights of October.

On offense, it's not the most potent lineup, but the middle-of-the-order group of Paul Goldschmidt, Tyler O'Neill, Nolan Arenado and Dylan Carlson has been rock solid, and Tommy Edman does a lot of little things at the top of the order. O'Neill has a .325/.391/.701 line in September that includes eight home runs and 20 RBI in 21 games.

It took the club a while to get rolling, but this team is legit.

Buy or Sell: Buy

Boston Red Sox

Playoff Chances: 96.3 percent

The Boston Red Sox won seven in a row heading into Thursday, and they close out the season with a three-game series against the Baltimore Orioles and three against another last-place club in the Washington Nationals.

That bodes well for their chances of holding on to a wild-card spot, but what then?

This team has used seven different starting pitchers in September while trying to chase down a playoff berth, and outside Nathan Eovaldi and a healthy Chris Sale, it's impossible to trust anyone on Boston's starting staff.

Losing multi-inning reliever Garrett Whitlock to a strained pectoral over the weekend was a huge blow. He's not expected to miss significant time, but his importance can't be overstated as he's tallied eight wins, two saves and 15 holds while posting a 1.99 ERA in 72.1 innings.

The offense will score plenty of runs, but it's difficult to view this team as a bona fide contender because of its two huge question marks in the postseason rotation.

Buy or Sell: Sell

Houston Astros

Playoff Chances: 100 percent

Love them or hate them, the Houston Astros are serious title threats once again.

A plus-220 run differential that trails only the Los Angeles Dodgers (+245) speaks to a well-rounded roster anchored by a high-powered offense and a terrific young rotation that has exceeded expectations.

Zack Greinke remains a solid veteran presence and Lance McCullers Jr. is living up to the five-year, $85 million extension he signed in March, but it's the unheralded trio of Framber Valdez, Jose Urquidy and rookie Luis Garcia that has made the rotation one of the best in baseball.

The offense leads the majors with 825 runs, good for 5.4 per game, and the core group of Carlos Correa, Jose Altuve, Alex Bregman and Yuli Gurriel remains steady, while rising stars Kyle Tucker and Yordan Alvarez have made that group even more potent.

The biggest question ahead of the trade deadline was the bullpen, and the trio of Kendall Graveman, Yimi Garcia and Phil Maton have helped stabilize things alongside All-Star Ryan Pressly. One of their three young starters will likely move to the bullpen in October, and that person could provide another wrinkle as a multi-inning weapon.

This might be the team to beat in the American League.

Buy or Sell: Buy

Chicago White Sox

Playoff Chances: 100 percent (clinched)

Can the Chicago White Sox flip the switch when the games start to matter again?

This team has had at least a nine-game lead in the AL Central since Aug. 1 and have been in complete control for most of the second half.

That inevitably leads a team to take its foot off the gas, whether it's in an effort to stay healthy for what could be an additional month of baseball or a general lack of urgency.

They struggled to a 36-39 record away from home and a 25-29 record against teams with a winning record, and much of the season has been spent beating up on a bad AL Central.

If Chicago can turn it on when it matters, the starting rotation of Lance Lynn, Lucas Giolito, Carlos Rodon and Dylan Cease can carry this team on a 2005-esque run, and there is no shortage of thunder in the lineup now that Luis Robert and Eloy Jimenez are healthy.

Buy or Sell: Buy

Tampa Bay Rays

Playoff Chances: 100 percent (clinched)

With Charlie Morton and Blake Snell departing during the offseason, Tyler Glasnow and Yonny Chirinos recovering from Tommy John surgery, and Rich Hill traded to the New York Mets at the deadline, the Tampa Bay Rays have been forced to get creative with piecing together a starting rotation.

Ryan Yarbrough leads the team with 144.1 innings pitched, and no one else has eclipsed the 120-inning mark. The left-hander is joined by 24-year-old Shane McClanahan, 22-year-old Shane Baz and 21-year-old Luis Patino, who are all rookies, along with reliever-turned-starter Drew Rasmussen.

Despite all of that, this team still has a solid 4.23 starters ERA, and that group is backed by the AL's best bullpen, which boasts a 3.25 ERA, 1.15 WHIP and 9.5 K/9.

The lineup packs more punch than in years past, led by Brandon Lowe (34 HR), Austin Meadows (26 HR, 103 RBI) and rookie phenom Wander Franco (once he returns from a hamstring strain).

Despite the non-traditional makeup of the pitching staff, this might be the most well-rounded Rays club we've seen in recent years.

A return to the Fall Classic is well within reach.

Buy or Sell: Buy

Milwaukee Brewers

Playoff Chances: 100 percent (clinched)

Barring something unexpected over the season's final two weeks, the Milwaukee Brewers are my pick to win the 2021 World Series.

Corbin Burnes, Brandon Woodruff and Freddy Peralta form a dominant trio atop the rotation capable of carrying this club throughout October, and back-of-the-rotation starters Eric Lauer and Adrian Houser have also been throwing extremely well during the second half.

That group is backed by a lethal bullpen contingent anchored by Josh Hader, Devin Williams and Brad Boxberger, and don't sleep on hard-throwing rookie Aaron Ashby as a major X-factor in a multi-inning role in October.

Offensively, this team has been transformed by the midseason additions of Willy Adames and Eduardo Escobar, and unsung contributors Avisail Garcia and Luis Urias continue to be huge in the middle of the lineup.

If the offense can do its part, the Brewers have the pitching to steamroll the competition in October.

Buy or Sell: Buy

Los Angeles Dodgers

Playoff Chances: 100 percent (clinched)

Even before they swung a deadline blockbuster to acquire Max Scherzer and Trea Turner from the Washington Nationals, the Los Angeles Dodgers were a serious threat to repeat as World Series champions.

Turner, the NL hits leader, is batting .307/.357/.458 with nine steals and 28 runs scored in 42 games since the trade while filling a hole at second base.

Scherzer, the NL Cy Young front-runner, has been virtually untouchable post-trade. The 37-year-old is 7-0 with a 0.78 ERA, 0.66 WHIP and a 79-to-7 strikeout-to-walk ratio in 58 innings in a Dodgers uniform and poised to anchor the staff in October.

Those two joined a stacked roster that has spent much of the year looking up at the San Francisco Giants in the NL West but may still be the team to beat once the records reset and it becomes a sprint to the World Series.

A rotation of Scherzer, Walker Buehler, Clayton Kershaw and Julio Urias will be awfully difficult to deal with and stacks up well against the arsenal of arms the Milwaukee Brewers bring.

Buy or Sell: Buy

San Francisco Giants

Playoff Chances: 100 percent (clinched)

After a 29-31 season a year ago, the San Francisco Giants looked more likely to battle for a .500 record and a distant third in the NL West race than they did to be legitimate contenders.

Their hot start was met with skepticism, and plenty of doubters remained when they entered the All-Star break two games up in the division with a 57-32 record, but they have continued to pile up wins while they try to hold on for their first division title since 2012.

The roster is built to platoon, much like the Dodgers have done in past years, and the bench has no wasted spots. The unexpected contributions of Darin Ruf, LaMonte Wade Jr. and Steven Duggar have provided a boost, while a return to All-Star form from veterans Buster Posey and Brandon Crawford has solidified the attack.

On the pitching side, a breakout season from Logan Webb alongside the veteran duo of Kevin Gausman and Anthony DeSclafani have made the rotation one of baseball's biggest surprises. The bullpen is MLB's best with a 3.12 ERA and 52 saves in 79 chances.

Does this team look like the World Series favorite on paper? Probably not, but it has exceeded expectations all year, and there's no reason to believe San Francisco won't continue to do so in the postseason.

Buy or Sell: Buy

All stats courtesy of Baseball Reference and FanGraphs, and accurate through Wednesday's games.