Which contenders’ bullpens are built to hold up for the stretch run?

Bullpen performance matters most as the season approaches its final month.

Relievers generally pitch the highest-leverage innings, and in October they often take on an even greater share of the work. The question is not simply which teams have the best bullpens. It's which bullpens are pitching well now, have the underlying stuff to sustain performance and are not being run into the ground.

I evaluated every bullpen using two broad dimensions: performance and freshness.

Performance was based on K-BB%, SIERA, FIP, Stuff+ and Location+, with more weight given to recent months.

Freshness incorporated innings, pitches and "pulls." (Pulls represent the number of times a pitcher is removed from a game, serving as a proxy for the accumulated stress of warming up and repeatedly entering games, often in high-leverage situations.)

The goal was to measure what pitchers are actually doing, rather than what has happened around them, and whether they've been overworked.

In going back to test the past three seasons, the model has recent predictive value. Six of the 10 bullpens that ranked best entering September remained among the 10 best in the final month. The April-August process score, weighted more heavily toward the second half, also had a 0.64 correlation with September performance.

That's hardly a guarantee, but for one of baseball's most volatile units, it's a meaningful signal.

As we approach the final month, seven of the 10 teams that rank best in the combined performance-and-freshness model are contenders: the Astros, Red Sox, Rays, Padres, Brewers, Cubs and Diamondbacks.

Let's evaluate some of the more interesting cases. (Note: Stats below are through Wednesday’s games.)

Hottest: Astros

No club has improved more than the Astros. Just consider their bullpen’s K-BB% (in other words, the gap between their strikeout and walk rates) by month:

April: 6.9%
May: 10%
June: 17.6%
July: 20.7%
August: 20.7%

The gains also align with strong trends in underlying Stuff+ and Location+ metrics. That's not a marginal improvement. It's a bullpen transforming from mediocre underlying performance into one of the league's strongest groups.

This makes sense, as the club didn't get longtime elite closer Josh Hader back healthy until June. Steven Okert has been even better in the second half than the first. And arms like Bennett Sousa have helped in middle relief.

The Astros are only middle-of-the-pack in bullpen volume, meaning the improvement isn't coming at the cost of an excessive workload. This could be a big deal for the Astros as they try to hang onto a slim lead over the Rangers in the AL West.

Best stuff, improving command: Padres

Mason Miller gives San Diego the league’s best bullpen anchor, and the supporting cast around him is doing a better job of harnessing its talent.

San Diego owns some of the best stuff in the game, including arms like Adrian Morejon touching 100 mph from the left side. But what's changed is their underlying command numbers, which have improved throughout the year, cutting their bullpen walk rate from 9.3% in the first half to 7.5% in the second, tied for fourth best in the Majors.

That isn't simply a results-based improvement: Their Location+ has climbed steadily from 99 in March-April to 104 in August.

The only thing going against San Diego is workload. The bullpen has thrown the fourth-most innings and pitches in August – this after being the only bullpen to throw more than 2,000 pitches in July.

This should continue to be an elite group, unless the workload begins to catch up with it.

Best balance, thinner roster: Red Sox

Boston enjoys the best combination of performance and lack of overuse among any contender to date. The model loves what Boston has done. The problem is the roster is less healthy than it was a month ago. The Red Sox have lost quality relief arms Justin Slaten and Garrett Whitlock to elbow injuries this month.

Tyron Guerrero, who owns a great story, has been excellent in a setup role, and Erik Miller was a crucial Trade Deadline acquisition to strengthen the late-game group in front of closer Aroldis Chapman. Are they enough? The group is thinner than it was when their excellent numbers were accumulated. That makes the Boston bullpen the biggest question mark among the contenders.

Getting stronger while staying fresh: Brewers

Thanks in large part to Jacob Misiorowski, the Brewers lead MLB in starting pitching WAR and expected ERA, and are second in actual ERA. That's a big help for a team trying to win the World Series. But its bullpen is another strength – and it's getting stronger.

The Brewers are enjoying their best month by K-BB% (17.1%), and entering play Thursday they had thrown the seventh-fewest pitches in August (989). This is after adding help at the Deadline in underrated Rockies reliever Antonio Senzatela. They have also moved starter Chad Patrick to the bullpen, adding further depth.

The Brewers enjoy a rare combination entering the final stretch: great stuff, improving performance and a bullpen that hasn't been asked to carry an excessive workload.

The picture is less encouraging for several other contenders.

Command trouble: Dodgers

For all of its resources and success, Los Angeles still hasn’t been able to achieve bullpen stability.

The team placed Edwin Díaz on the IL for a second time this season Tuesday with a neck issue, after his velocity was down during another poor outing. But the problem is bigger than Díaz. Manager Dave Roberts acknowledged last week he does not have a depth of elite options.

"Give me another option. I can’t just say change [and use Díaz] in lower leverage; I have to have other options," Roberts told reporters. "And to be quite honest, none of those guys really are throwing the baseball great. So that’s just kind of the way it is."

It's not a stuff problem in Los Angeles. It's a command issue. The Dodgers' Location+ scores of 93 in July and 94 in August ranked 29th and 28th in MLB, respectively. That has coincided with a 12% walk rate in the second half – the highest in the Majors.

It's difficult to see how the Dodgers fix this in short order. While they can move a starter or two to their beleaguered bullpen in October, ideally they still need to secure a first-round bye to give themselves the best shot at a three-peat.

Workload finally showing up: White Sox

Since July 1, White Sox relievers have combined for 3,278 pitches thrown, the most in the Majors. Only three other teams have reached 3,000: the Padres, Pirates and A’s.

The Sox are the Cinderella story of the 2026 season, but bullpen usage is threatening to move the clock to midnight. The good news? In recent years, evaluating innings, pitches and "pulls" has not been as predictive of a September faltering as skill. Massive workload alone isn't fatal.

Still, there's reason for concern. Chicago relievers' K-BB% fell dramatically this month, from over 14% in each of the previous three months to 10.9% in August. Their underlying Stuff+ also sits at a season-worst 97 this month.

A lot of arrows are pointing up in Chicago, but one pointing down is bullpen performance.

A strength becoming a weakness: Guardians

Cleveland's recent success has often been built on an elite bullpen. But this year's group is moving in the opposite direction.

Cleveland's bullpen performance has generally declined month over month this season, producing season-worst marks in ERA (5.24), FIP (4.97), K-BB% (12.5%), Stuff+ (102) and Location+ (92) in August – the latter an MLB worst.

To have any hope of catching the White Sox in the AL Central, or a final Wild Card spot, this group will once again have to become a strength.

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Bullpens are among the most chaotic units in baseball, so no model can eliminate the uncertainty.

But recent performance, underlying skill and workload can provide useful clues about which teams are best positioned for the high-leverage innings of the stretch run, when the end-game arms matter most.