The final push of the 2017 Major League Baseball season means the game's biggest stars are having their clutch genes put to the test.

The Bleacher Report MLB Metrics 101 is watching.

Hello and welcome back. This week's topic is a game of "Clutch or Choke" with the biggest stars of the MLB postseason race. Here are the ground rules:

• The best player from each of the six division leaders and four wild-card leaders, as determined by FanGraphs WAR, is under the microscope.
• Baseball Reference WAR is usually the go-to around these parts, but FanGraphs gets the nod this week because they allow for more detailed splits. That comes in handy in this case because...
• Players will be judged on the quality of their performances—both overall via WAR (including RA-9 WAR for pitchers) and in context via WPA (Win Probability Added)—over the last 30 days, which covers both high-pressure August games and higher-pressure September games.
• Stats are current through Tuesday, September 19.

What you'll see is players' 30-day WAR and WPA on their own, and also how much of their full-season WAR and WPA these figures account for.

Since 30 days out of 171 in-season days ticked off so far is 18 percent, that's a helpful guideline for whether players have been living large or small. But it will indeed be more of a guideline than a rigid rule. Ultimately, whether players deserve a "Clutch" or "Choke" label is a judgment call.

Starting in the AL East and going from there, let's get to it.

Choke: Chris Sale, Boston Red Sox

Among the many reasons the Boston Red Sox are struggling to outrun the New York Yankees in the AL East: Their ace isn't pitching like an ace.

With a 2.37 ERA and a whopping 211 strikeouts through the end of July, Chris Sale seemed well on his way to winning the American League Cy Young Award. But his season has since turned into a struggle, especially recently.

Sale has a 4.50 ERA in five starts since August 24. In the mix are duds against the Cleveland Indians, Yankees and, most recently, the Tampa Bay Rays in which he was none too happy with an early hook.

"I want to be out there as long as I can and eat up as many innings as I can, save the guys in the bullpen, stuff like that. But I did it to myself," the left-hander said, per Jason Mastrodonato of the Boston Herald.

There's still time for Sale to right the ship, of course. And if he's going to do so, the eight-inning, 13-strikeout gem he tossed against the Baltimore Orioles on Wednesday is a heck of a way to start.

Verdict: Choke

Clutch: Corey Kluber, Cleveland Indians

As one AL Cy Young contender fades, another rises.

Corey Kluber is hotter than Sale and any pitcher in this or any other known universe. His 1.35 ERA in six starts since August 23 comes out to 2.8 WAR, the most of any pitcher over the last 30 days.

Kluber's WPA, meanwhile, is boosted by how he's clamped down when the pressure has been highest. His last six starts have churned out 19 high-leverage plate appearances against him. Only two turned into run-scoring hits, compared to 14 outs.

What makes all this even scarier is that it's a mere slice of a larger hot streak. Kluber has been smoking ever since coming off the disabled list June 1, posting a 1.69 ERA and permitting just a .482 OPS in 21 starts.

Given that they recently won 22 games in a row, it's not surprising Kluber isn't the only member of the Indians who deserves props for his late-season performance. Between their hitters and pitchers, they're a whole team of hot players.

Verdict: Clutch

Choke: Jose Altuve, Houston Astros

It's not every day there's a reason to criticize Jose Altuve.

With a .271/.333/.506 slash line and five home runs, Altuve hasn't been bad over the last 30 days. And as his WPA indicates, he's provided some important hits.

Take his five homers, for example. Only two were solo shots, and all five gave his Houston Astros either a tie or the lead. The most recent of these happened just Tuesday when he launched a game-tying solo homer off Chicago White Sox right-hander Lucas Giolito in the fourth inning.

There is, however, no doubt Altuve set a high bar for himself over the first four-plus months of the season and is now struggling to clear it. He hasn't been bad, but he also hasn't been Altuve-level great.

It's not a huge deal regarding Houston's postseason chances—its first AL West title is already in the bag—but it's no help in the AL MVP race. Altuve has opened the door for red-hot hitters like Jose Ramirez and Francisco Lindor to get more attention. And, of course, nobody can rule out Mike Trout.

Verdict: Choke

Clutch: Aaron Judge, New York Yankees

If one was so inclined, one could just as easily label Aaron Judge a late-season choker.

He's mostly been good over the last 30 days, putting up a .247/.411/.553 slash line with seven homers over 26 games. But as his WPA indicates, he hasn't been able to ditch a caveat that's dogged his entire season.

The young Yankees slugger landed in MLB Metrics 101's recent expose on baseball's least clutch hitters due to his tendency to do damage outside high-leverage situations. And so it goes. In the 18 high-leverage situations he's faced since August 24, he has two walks (one intentional) and nothing else.

Still, this is a case where the numbers warrant a finger wag but not a full-on scolding.

Judge was still pulling out of his lengthy post-All-Star slump at the end of August but has been a new man in September with a 1.080 OPS and all seven of the aforementioned dingers. That's way too much production to call a guy a choker.

Plus, it's been a boost for a Yankees team that's rolling with a 13-5 record this month. As per usual, they wouldn't be where they are without Judge.

Verdict: Clutch

Clutch: Ervin Santana, Minnesota Twins

The notion that Ervin Santana could ever be any team's best player sounds a bit off. Yet here we are.

The Minnesota Twins have had players rise and fall all season, but Santana has been a steady hand who's produced a 3.34 ERA over 199.1 innings. While he peaked early, he hasn't so much slumped as leveled off. That includes his latest efforts, as he's cruising right along with a 3.41 ERA over his last six starts.

The one "Yeah, but" is that he's made two starts each against the White Sox and Kansas City Royals and another against the San Diego Padres. The Yankees are the only tough opponent he's faced, and he took a loss against them September 18.

"I want to pitch better than this one," the veteran said afterward, per Rhett Bollinger of MLB.com. "If I get the chance to come here again, we just have to win, no matter how."

But in allowing only two earned runs across 5.2 innings, Santana hardly bombed against the Yankees. That gets at the essential truth of his 2017 season, both now and always:

If the Twins are going to lose, it's not going to be because of him.

Verdict: Clutch

Clutch: Anthony Rendon, Washington Nationals

At least for FanGraphs WAR, Anthony Rendon has been the best player in the National League this year. That ought to help his case for NL MVP.

In the meantime, he isn't hurting his case in the home stretch. He's hit a rock-solid .333/.404/.529 over the last 30 days and has really been heating up with a .357/.426/.619 slash line over his last 11 games.

One obligatory note is that this is a course correction for the unheralded star. He was riding high through July but then fell into a pit in August. He's just now digging himself out of it.

Still another obligatory note is that it's Stephen Strasburg who's been the Washington Nationals' best player in recent days. Since coming off his latest stay on the disabled list August 19, he's been nigh unhittable with a 0.66 ERA over six starts.

Still, this is no cause to label Rendon a choker. He's playing as well now as he has all season, and his play has already helped the Nationals sew up their second straight NL East title.

Verdict: Clutch

Clutch: Kris Bryant, Chicago Cubs

Finally! An excuse to slap the ol' "Clutch" label on Kris Bryant.

The former No. 2 pick, Minor League Player of the Year, Rookie of the Year and MVP has made a heck of a name for himself in short order. But the big nit to pick has been his performance in the clutch, as he's been the least clutch hitter of them all over the last two seasons.

He's now fighting back against that narrative.

Beyond having a .297/.416/.527 slash line overall in the last 30 days, he's done well for himself in high-leverage situations. He's faced 19 of them and has produced three walks and six hits, including a big three-run homer off New York Mets right-hander Robert Gsellman on September 12.

It's all been a boon to the Chicago Cubs.

After cake-walking their way to an NL Central title last year, they've needed all the help they can get this season. While it hasn't been easy, Bryant's hitting is one reason why they're trending toward a hard-won division title.

Verdict: Clutch

Choke: Clayton Kershaw, Los Angeles Dodgers

In addition to "Choke," another way to read Clayton Kershaw's recent performance is "Guy Who Literally Just Came Off the DL."

For the second time in as many years, the three-time Cy Young winner was sidelined for over a month with a bad back. He hasn't been terrible since his return September 1 but has been decidedly un-Kershaw-like with a 3.74 ERA over four largely unimpressive starts.

The low-light came Monday when he gave up his first-ever grand slam to Philadelphia Phillies youngster Aaron Altherr. Afterward, Kershaw didn't bother trying to contain his frustration.

"No progress," the lefty told reporters when asked about any potential bright spots. "We had the lead, and I blew it, and we lost, so there's not a lot of progress there to be had. Just go back to the drawing board and figure it out for the next one."

With the NL West race all but won, the Dodgers don't need to be in panic mode over the condition of their ace. But since they'll need his help to get through the postseason, at least a little concern is warranted.

Verdict: Choke

Clutch: Zack Greinke, Arizona Diamondbacks

Meanwhile, in the desert, Kershaw's former rotation mate is doing just fine.

Zack Greinke's entire season has been a complete 180 from the thud with which he landed in his 2016 debut with the Arizona Diamondbacks. And it's only getting better as the clock ticks down. In five starts dating back to August 25, he has a 1.56 ERA over 34.2 innings.

Because he's faced a whopping 26 high-leverage situations, there have been plenty of chances for Greinke's hot streak to come tumbling down. But these have produced just one run-scoring hit and 21 outs.

While he's had the luxury of facing the San Francisco Giants twice, his other three starts were against the Los Angeles Dodgers (twice) and Colorado Rockies. He dominated in all three, thereby making the NL West race difficult for the Dodgers and the NL wild-card race difficult for the Rockies.

It's a foregone conclusion at this point that the D-backs will take the NL's top wild-card spot. Assuming they do, Greinke would have the chance to make dominating the play-in game the next act of a terrific season.

Verdict: Clutch

Clutch: Charlie Blackmon, Colorado Rockies

The fact that Nolan Arenado isn't listed as the Colorado Rockies' best player might seem like a mistake. But it's not, and that's as good a compliment as any to the season Charlie Blackmon is having.

He leads the NL in batting average at .332 and all of MLB with 200 hits, 131 runs scored and 367 total bases. To boot, he's doing all this while holding down a premium position in center field.

At present, Blackmon isn't the hottest he's been all season. But there's little to nitpick about a .311/.398/.553 slash line over a 30-day period, particularly when there are big hits in the mix. He's collected four run-scoring hits in high-leverage situations, including a clutch go-ahead homer August 26.

It's all been in service to a Rockies offense that's been good-not-great with a collective .770 OPS over the last 30 days. To give credit where it's due, Arenado, DJ LeMahieu and Carlos Gonzalez are also helping to carry the club's lineup.

If they can hold on just a little longer, the Rockies will be playing in October for the first time since 2009.

Verdict: Clutch

Data courtesy of FanGraphs and Baseball Reference.