The MLB Playoffs Are a Whole New Ballgame—Or At Least One With Different Ballplayers

As you may have heard , the MLB playoffs are unpredictable. The results are inscrutable, compared to the regular season, because October conditions are different. The teams are typically pretty evenly matched. The series are short, and the samples are small. The pressure is high; the air is cold; and the players are intensively scouted , extra fatigued, and playing through pain . But there's another, underrated reason it's tough to anticipate how teams will play in October: It's also increasingly tough to anticipate who will play for them.

Down 2-0 in the ALCS entering Thursday's Game 3, the Cleveland Guardians handed the ball to left-handed starter Matthew Boyd, who's better known for his time on a different AL Central team . The 33-year-old, who had Tommy John surgery in June 2023, signed with Cleveland as a free agent almost exactly one year later and made his 2024 major league debut in mid-August. He started only eight big league games during the regular season, but drew the starting straw in three of Cleveland's first eight October contests.

Boyd, who held the Yankees to one run over five innings to lay the groundwork for a wild Game 3 win, was more of a regular-season staple for Cleveland than another of the club's go-to starters this month, Alex Cobb. The Guardians acquired the 37-year-old from the Giants at the trade deadline, after recovery from hip surgery and subsequent shoulder problems had kept him off major league mounds all season. Nail and finger trouble limited him to just three starts down the stretch, but that didn't dissuade the Guardians from entrusting him with starts in ALDS Game 3—his first postseason appearance in 11 years —and ALCS Game 1. The oft-injured righty likely would have matched his regular-season-starts total with a third postseason nod this week had he not hurt his back and been replaced on the roster .

The substitute for Cobb, Ben Lively, made the second-most starts on the team in the regular season (29) but was left off the ALDS roster (and, initially, the ALCS one), which he said " stung ." The third-, fourth-, and sixth-most-prolific regular-season starters—Carlos Carrasco, Logan Allen, and Triston McKenzie—were demoted to the minors before the end of the season; Gavin Williams and Joey Cantillo, who ranked fifth and seventh, have been in the bullpen this month. (Williams will start Game 4, though as of Friday morning, the Game 5 gig was still listed as assigned to October's busiest starter, "TBD.")

In part, the October turnover in the Guardians' rotation reflects the weakness of the team's starting staff, which lost presumptive ace Shane Bieber to Tommy John surgery in April and went on to finish 27th and 29th , respectively, in FanGraphs and Baseball-Reference WAR. Boyd and Cobb tied for the lowest FIP recorded by any hurler who made more than two starts for Cleveland, which made them appealing alternatives to almost any incumbent. Plus, whoever serves as starter for Cleveland rarely lasts long: The Guardians boast one of the best bullpens ever, and rookie skipper Stephen Vogt has had an accordingly quick hook. Until Boyd's outing on Thursday, no Guardians starter had made it through five innings this month, and even no. 1 starter Tanner Bibee was yanked after four outs in Game 2. All told, Cleveland's starters have pitched 39 percent of the team's postseason innings, even lower than the " pitching chaos " Tigers' rate.

Still, this preference for change candidates —which also extends to September call-ups Erik Sabrowski and Andrew Walters, who have leapfrogged regular-season stalwarts Pedro Avila and Nick Sandlin in the bullpen pecking order—may be a microcosm of a larger philosophical shift in teams' approach to the postseason. As Joe Sheehan observed in his newsletter last week:

It certainly seems as if playoff-bound teams have grown less likely to dance with the ones that brung them. Think back to last year, when Twins reliever Chris Paddack pitched as many times in the ALDS (twice) as he did during the regular season; the Phillies anointed rookie Orion Kerkering a postseason setup man after all of three regular-season innings; the Diamondbacks depended on a rebuilt bullpen, featuring late-season additions Andrew Saalfrank and Ryan Thompson, to propel them to a pennant; and the Rangers rode September call-up Evan Carter's hot hitting to a title. On the other end of the surprise-usage spectrum, Phillies starter Taijuan Walker, who had led the team in pitcher wins and ranked second (Baseball-Reference) or third (FanGraphs) in WAR, didn't appear in the playoffs—which he wasn't pleased about—after fading late in the year. As Walker's teammate Nick Castellanos said last October, "I'm learning that the season and the postseason are completely different."

We haven't seen any more major league debuts or rookie breakouts in this year's postseason, but the Dodgers have carried a couple of late-season call-ups (Ben Casparius and Edgardo Henriquez, the latter of whom started the season in A ball), the Mets opted for a fresh-off-the-minor-league-lot Luisangel Acuña over veteran reliever Adam Ottavino, and the Yankees gave Jon Berti his first professional start at first base. (According to Kenny Jackelen of Baseball-Reference, Berti is only the third player on record to start at a position for the first time as a pro in the playoffs, following Miguel Cabrera in right field for the 2003 Marlins and Buddy Myer at third base for the 1925 Nationals.) We've also seen teams bypass big-name veterans—the Astros omitted Justin Verlander from their ALDS roster, as the Yankees did Marcus Stroman—or roll the dice with players returning from extended injury absences, such as Cobb and Kodai Senga. (The Dodgers even considered activating Tony Gonsolin, who hasn't pitched in the big leagues this year.)

There are a couple of ways we can assess whether teams have been making these " really hard decisions " more often. One is by adapting a method I've previously used to study roster turnover across seasons. The table below, built from Retrosheet data crunched by Ryan Nelson , shows the percentage of regular-season playing time—as measured by combined plate appearances and batters faced—produced by the players on playoff-bound teams who went on to appear in the postseason. The lower the percentage, the less consistency between regular-season and postseason rosters. (The results are broken down by decade to increase the size of the samples; since this year's playoffs are incomplete, the rates for the 2020s exclude 2024.)

Sure enough, the division series, championship series, and World Series rates for the 2010s and 2020s are lower than those of earlier decades. In the 1970s, the high-water mark for this formulation of roster consistency, players who appeared in the postseason had amassed 91 percent of their teams' regular-season playing time; only 9 percent of regular-season reps went to players who were absent in October. In the first four World Series of the 2020s, postseason players accounted for only 82 percent of regular-season opportunities, meaning that twice as much regular-season playing time went to non-postseason players as in the 1970s. The changes aren't enormous, but they're there.

What this method can't quite account for is differences in the roles of players who cracked a team's roster in both the regular season and the postseason. Take Lively, for instance: During the regular season, he faced 10.7 percent of the batters who stepped in against the Guardians. In the playoffs so far, he's faced six of 300 (2.0 percent). However, he has pitched in the postseason, so this one-size-fits-all approach would classify him the same as, say, setup man Cade Smith, who's more than doubled his usage rate from 4.9 percent in the regular season to 10 percent in the postseason. Ideally, we could account not only for whether players appeared in both the regular season and the postseason, but how prominent a part they played in each period.

For that, we've gotta get wonkier, with a two-proportion Z-test , a statistical assessment of the difference between the proportions of two groups (in this case, regular-season players and postseason players). This technique is typically reserved for use with independent, non-overlapping populations, unlike our groups of players, but it's sufficient for the purpose of measuring the magnitude of disparities in playing time. The higher the weighted-average Z-score, the more pronounced the increase in a player's share of his team's plate appearances and/or batters faced from the regular season to the postseason. It's difficult to describe this method in more detail in a non-mind-numbing way, so why don't we look at leaderboards and a chart?

The table below, based on data supplied by Nelson, lists the players whose share of playing time grew most significantly when the playoffs rolled around.

The top names on this list came by their postseason-playing-time windfalls via very different routes. Tigers pitcher Virgil Trucks missed all of the 1944 season, and almost all of '45, while he was serving (and playing exhibition baseball) in the Navy during World War II. He was discharged in time to make a single start in Detroit's last game of the regular season. Tune-up complete, he then started Games 2 and 6 of the World Series as Detroit defeated the Cubs.

Trucks spent most of 1944 in the South Pacific; Matt Moore spent most of 2011 in the Southern League. The young lefty, whom some sources would rank ahead of Bryce Harper and Mike Trout as the sport's top prospect entering 2012, made his major league debut for the Rays in September 2011. He threw 9 1/3 innings at the tail end of the regular season, then topped that with 10 frames in the ALDS.

The next player on the list, Justin Verlander, joined the 2017 Astros in a last - second trade at the August 31 waiver deadline and became a mainstay of their rotation en route to the team's tainted title. Then there's Francisco Rodríguez, the epitome of the postseason pop-up reliever, who took the 2002 playoffs by storm after a five-game cameo at the end of the regular season. In the postseason, Rodríguez more than tripled his regular-season innings total, accruing by far the heaviest workload of any playoff reliever (with a 1.93 ERA) as the Angels went all the way. K-Rod's debut helped clarify the rules around postseason eligibility, paving a path for many more players in subsequent years to appear on postseason rosters even if they didn't debut until after the traditional August 31 deadline for playoff eligibility, provided they were placed on their team's 40-man roster prior to September. After Rodríguez come Tyler Glasnow and Stroman, who in 2022 and 2015, respectively, returned from major surgeries just in time to take regular rotation turns in October.

I'll spare you the list of postseason playing-time losers—though you can scan it here —but I'll tell you the top playoffs snub: Jason Marquis, who led 2006 Cardinals pitchers with 33 games started but also led National League pitchers in losses and homers, and major league pitchers in earned runs. Dropping Marquis, who didn't appear in the postseason, was a wise move for St. Louis, as the 83-win team transformed into a World Series winner. (Five years later, Cardinals manager Tony La Russa would win another championship with an ahead-of-its-time reliance on relievers .) Similarly, if you'd like to look at a list of teams, you can find it here , ordered from least consistent to most consistent. Eight of the 25 least consistent teams with a minimum of five postseason games—including last year's Rangers, who rank third—played in the past decade; none of the most consistent teams did.

Which suggests that it's time to bring in the closer: a graph that shows how player-usage consistency on a team level has evolved during the wild-card era. A team with no change in playing-time apportionment between the regular season and postseason would have a weighted Z-score of zero; the leaguewide average is always higher than that, thanks to in-season acquisitions, injuries, and the natural tendency for teams to work their best players harder in October, when the games matter more and the travel-day-filled schedule affords more rest between contests. On the whole, though, the trend has been toward more change over time, no matter how long-lasting a team's playoff run.

So, yes: Postseason rosters and usage patterns look less like their regular-season counterparts than they used to. There could be a bunch of reasons for that: more injuries ; more midseason transactions and roster reshuffling; more pre-playoffs load management. But it's almost certainly also a product of teams taking a more aggressive approach to October—and, as they now do in free agency, evaluating players based less on what they've done before and more on what they're projected to do next. As the game gets younger, players approach their peaks more quickly, and the value placed on previous playoff experience shrinks, teams are growing increasingly willing to welcome new debutants to October, aided by a 2014 rule relaxation that made K-Rod-esque scenarios even easier to swing. ( Roster rules now allow players to substitute for someone on the injured list and appear in the postseason as long as they were in the playoff team's organization prior to September, regardless of whether they were on the 40-man.)

After the 2016 World Series, Dave Cameron posed a philosophical question in the form of a FanGraphs post : "Is the postseason becoming too different?" Cameron, who in earlier years had advocated for throwing out the regular-season script in October, was wondering whether teams had taken that prescription too much to heart, as Cleveland's usage of relief ace Andrew Miller broke bullpen barriers. "It was only a matter of time before the incentives to win overcame the notion that relievers could only be used in the way they were deployed in the regular season," Cameron wrote.

At this point, we could probably replace "relievers" with "players." As Cameron—now an executive for the Mariners—continued, "How far away from regular season baseball are we comfortable letting postseason baseball get? ... Is there a point at which we'll wonder if October baseball is just too different from the one teams have to play in order to get there?" If there is such a point, we're closer to it now than we were then.