The Bullpen Game Is Winning the World Series

Starters Are Pitching Less in October

In the 2015 postseason, starting pitchers averaged 5.8 innings per start. By 2024, that number dropped to 4.6 innings. Starters faced the lineup 2.3 times on average before being pulled. A decade earlier, the number was 2.7. Managers are pulling starters earlier, leaning on bullpens harder, and the results back them up.

The logic is straightforward. When a starter faces a lineup for the third time, opponent batting average jumps by 30-40 points. The third-time-through penalty is one of the most reliable effects in baseball. Postseason managers, facing elimination and operating without rest-day luxury, cannot afford that penalty. They go to the bullpen.

That 1.2-inning decline means the bullpen now covers 4.4 innings per postseason game on average, up from 3.2 in 2015. That extra inning-plus shifted onto the bullpen's shoulders is the difference between needing four good relievers and needing seven.

Five World Series, Five Bullpen Winners

From 2020 through 2024, every World Series champion ranked in the top 5 in postseason bullpen ERA. Three of the five ranked first. The correlation between postseason bullpen ERA and series outcome was stronger than the correlation with starting pitching ERA, team OPS, or regular season win total.

The 2024 Dodgers are the clearest case. Their starting rotation was decimated by injuries. In the postseason, Dodger starters posted a 4.12 ERA, 8th among playoff teams. Their bullpen posted a 2.56 ERA, the best in the bracket. The bullpen carried a championship team whose rotation would have been a liability in any other era.

The 2021 Braves offer another angle. Atlanta's starters posted a 3.89 ERA in the playoffs, middle of the pack. Their bullpen was the best in baseball at 2.44. In their four World Series wins, Braves relievers threw 17.1 innings with 2 earned runs. The rotation set the table. The bullpen cleared it.

The Strategy That Changed October

The formal bullpen game, where a team starts a reliever or opener with the intention of using 4-6 pitchers to cover 9 innings, appeared in the postseason in 2018 when the Brewers used it against the Dodgers in the NLCS. By 2024, every playoff team deployed at least one bullpen game during their postseason run.

Bullpen games work in October because they exploit the third-time-through penalty without any downside. Each reliever faces 3-6 batters, throws his best pitch at maximum effort, and hands off to the next arm. Hitters never get comfortable. They adjust to one pitcher's release point and velocity, then face a completely different look.

The 61% win rate overstates bullpen-game quality slightly, because teams deploy them selectively and sometimes in favorable matchups. But even after adjusting for opponent quality and home/away splits, bullpen games outperformed the replacement-level starter option (a 5th starter or spot starter) by roughly 0.8 runs per 9 innings.

Building a Postseason Bullpen

Teams that win in October build bullpens with specific characteristics. The data points to three traits that separate postseason-caliber bullpens from the rest: strikeout rate, platoon flexibility, and fresh-arm depth.

Strikeout rate matters most. In the postseason, contact is more dangerous because lineups are stacked with above-average hitters. A reliever who allows contact against a playoff lineup gives up harder contact than the same pitcher would face in July against a .500 team. Championship bullpens average 28%+ strikeout rates in the postseason. Non-championship bullpens average 23%.

Platoon flexibility is the second factor. Managers need relievers who can handle both lefties and righties. A reliever who dominates same-side hitters but gets crushed by opposite-side bats forces the manager into predictable matchup patterns. The 3-batter minimum rule, introduced in 2020, made platoon flexibility even more critical because pitchers can no longer duck unfavorable matchups.

Fresh-arm depth is the third. A 7-game series requires 8-10 reliable relievers. Teams that enter the postseason with 6 trustworthy arms and 2 question marks face compounding fatigue by Game 5. The 2022 Astros carried 13 pitchers on their postseason roster and used 11 in relief roles. Depth won the series as much as talent did.

What October Bullpen Management Requires

Building a championship bullpen is expensive in ways that do not show up on the payroll sheet. The primary cost is regular-season innings. To have 8-10 fresh arms in October, teams must manage workloads starting in June. That means using starters deeper into games during the regular season, carrying extra relievers, and strategically resting high-leverage arms during low-leverage stretches.

The Astros and Dodgers have been the best at this. Both organizations track cumulative pitcher workload with proprietary fatigue models that account for pitch count, pitch type, rest days, and velocity trends. By September, their highest-leverage relievers have thrown fewer innings than comparable arms on other teams, giving them a freshness edge that compounds over a playoff run.

The trade deadline has become a bullpen acquisition event. In 2024, 14 of the 20 most-traded pitchers at the deadline were relievers. Teams no longer trade for a rental starter to eat innings. They trade for a reliever who can eat the 6th and 7th innings in October, protecting the closer and the setup man from overwork.

October Belongs to the Bullpen

The trend will not reverse. Starting pitcher workloads continue to decline. Velocity continues to rise, and velocity correlates with shorter outings because high-effort pitching fatigues arms faster. The pitch clock has slightly increased pace of play but has not changed the fundamental pattern of shorter starts and longer bullpen sessions.

Teams that still build October strategies around a top-heavy rotation are fighting a war with last decade's weapons. The 2024 Dodgers proved that a mediocre rotation can win a championship if the bullpen is elite. The 2021 Braves proved it before them. The sample grows every year.

The next edge in postseason construction will be bullpen specialization. We are already seeing teams develop relievers for specific roles: the high-fastball pitcher who gets strikeouts in the 6th, the ground-ball artist who gets double plays with runners on, the max-effort closer who throws 4 pitches at 98+ for one inning. The future postseason roster is not 5 starters and 8 relievers. It is 3 starters and 10 specialists.

Sources & Data

Jesse Walker

Jesse Walker writes about baseball through data. He played outfield in high school, found his real position behind a spreadsheet, and hasn't stopped building models since.