Yes. MLB teams are allowed to change their postseason roster between playoff rounds.
Before every round — the Wild Card Series, Division Series, League Championship Series and World Series — a team submits a new 26-man postseason roster. That means a player who is left off the roster for one round can be added for the next, as long as he is postseason-eligible. [MLB]
Teams commonly use that flexibility to adjust their pitching staffs, add or remove bench players, account for injuries and build a roster that better matches the opponent or the length of the upcoming series.
Can MLB Teams Change Their Roster After Every Playoff Round?
Yes.
MLB requires teams to submit a 26-player roster before each postseason round. The roster does not have to be identical to the one used in the previous round. [MLB]
For example, a team could use one group of 26 players during the Wild Card Series and make several changes before beginning the Division Series.
The same process applies again before the League Championship Series and World Series.
Why Would A Team Change Its Playoff Roster?
Postseason roster construction can change considerably depending on the length and structure of a series.
A best-of-three Wild Card Series does not necessarily require the same roster composition as a best-of-seven World Series.
A team might make changes because:
- A starting pitcher will not be needed in the next round.
- A team wants an additional relief pitcher.
- A player has recovered from an injury.
- A player was injured in the previous series.
- A team wants another left-handed or right-handed hitter.
- A pinch-running specialist could be valuable.
- A defensive replacement better fits the upcoming opponent.
- The opposing team’s pitching staff creates a favorable matchup for a particular hitter.
Because MLB treats each postseason round as a separate roster period, clubs can make those strategic adjustments before the next series begins. [MLB]
Can A Player Be Left Off One Round And Added For The Next?
Yes.
A player does not have to appear on every postseason roster to remain eligible for later rounds.
For example, a pitcher could be left off the Wild Card roster because the team expects to use only three starters and then be added for a five-game Division Series.
Similarly, a position player could be left off one round and restored for the next if the team’s matchup or roster needs change.
The important requirement is that the player must otherwise satisfy MLB’s postseason eligibility rules. [MLB]
How Many Players Are On An MLB Postseason Roster?
Each postseason roster contains 26 players.
MLB increased the postseason roster limit from 25 to 26 beginning in 2020. [MLB]
Unlike September regular-season rosters, which expand to 28 players, postseason teams return to a 26-player active roster.
Can Teams Change The Roster During A Playoff Series?
Generally, not for strategic reasons.
Once a postseason series begins, the 26-man roster is effectively locked for that round.
A manager cannot simply remove a struggling hitter or tired relief pitcher midway through the series and replace him with another player.
The primary exception is injury.
What Happens If A Player Gets Injured During A Playoff Series?
A team can request permission from the Commissioner’s Office to replace a player who becomes injured during a postseason series. [MLB]
If MLB approves the replacement, another postseason-eligible player can be added to the active roster.
However, there is an important penalty attached to that move.
What Happens To A Player Who Is Replaced Because Of Injury?
A player removed from a postseason roster because of injury becomes ineligible for:
- The remainder of the current series, and
- The entire following postseason round.
That restriction prevents teams from using the injury replacement rule as a way to make ordinary tactical roster changes during a series. [MLB]
For example, if a player is replaced because of injury during the Division Series, he cannot return during that Division Series and also cannot participate in the League Championship Series.
If his team advances again, he could potentially return for the World Series if he is healthy and otherwise eligible.
Can A Pitcher Replace An Injured Position Player?
No.
MLB requires injury replacements to remain within the same broad roster category.
- An injured pitcher must be replaced by another pitcher.
- An injured position player must be replaced by another position player.
This prevents a team from claiming an injury simply to alter the balance between pitchers and hitters on its roster. [MLB]
Can A Team Change From 12 Pitchers To 13 Pitchers Between Rounds?
Yes.
Because teams submit an entirely new roster before each postseason round, they can change the makeup of the roster.
A club could carry 12 pitchers during one round and 13 during the next if its strategy changes.
That decision often depends on the length of the series and the scheduling of off days.
Why Might A Wild Card Team Carry Fewer Pitchers?
The Wild Card Series is only best-of-three and is played on consecutive days.
A team knows it can play a maximum of three games, which means it may not need all of the starting pitchers it would normally carry during a longer series.
A fourth or fifth starter who is unlikely to pitch might be left off the Wild Card roster in favor of:
- An additional relief pitcher
- A pinch hitter
- A pinch runner
- A defensive specialist
- A third catcher
If the team advances to the Division Series, that starting pitcher can then be added to the new roster.
Why Would Teams Add More Pitchers For A Longer Series?
The Division Series can last five games, while the League Championship Series and World Series can each last seven.
Longer series create more innings and more opportunities for pitching fatigue.
A team that could operate with three starters during the Wild Card round may need four starters in a seven-game series.
That can make postseason roster construction very different from round to round.
Who Is Eligible For An MLB Postseason Roster?
Postseason eligibility is generally determined at the end of August.
Players must normally have been part of the organization and in an eligible roster status by 11:59 p.m. ET on August 31 to participate in the postseason. [MLB]
The rule prevents a playoff team from signing or acquiring outside players in September specifically to strengthen its postseason roster.
Can A September Trade Acquisition Play In The Postseason?
Normally, no.
A player acquired after the August 31 postseason eligibility deadline generally cannot be placed on that team’s playoff roster.
That is one reason contenders try to complete important trades before the postseason eligibility deadline.
Can A September Call-Up Play In The Playoffs?
Potentially, yes.
Being called up to the major leagues in September does not automatically make a player ineligible.
The key question is whether the player satisfied MLB’s postseason eligibility requirements by the August 31 deadline.
A player could therefore spend much of the season in the minors, get promoted in September and still appear in the postseason if he was already part of the organization and met the necessary roster requirements.
Can A Player Return From The Injured List For A Later Round?
Yes, if he is healthy, eligible and has satisfied the applicable injured-list requirements.
A team might begin the postseason without an injured player, advance through one or more rounds and then activate him for a later series.
Because a new postseason roster is submitted before each round, the player can be added once he is eligible to return.
What If A Star Player Gets Hurt In The Wild Card Series?
Suppose a team’s starting shortstop suffers a serious injury during Game 1 of the Wild Card Series.
The club could request permission from MLB to replace him with another postseason-eligible position player.
If approved:
- The replacement can play immediately.
- The injured shortstop cannot return for the remainder of the Wild Card Series.
- The injured shortstop also cannot play in the Division Series if the team advances.
That consequence makes teams cautious about requesting an injury substitution for players who might recover quickly. [MLB]
Can A Team Just Declare A Player Injured To Replace Him?
No.
The club must request approval from MLB’s Commissioner’s Office.
The rule is designed specifically for legitimate injuries rather than poor performance or matchup decisions. [MLB]
A manager therefore cannot replace a pitcher simply because he gave up several runs or remove a hitter because he is struggling at the plate.
Can An Injured Player Return In The Same Series?
No.
Once an injured player has officially been replaced on the postseason roster, he is ineligible for the rest of that series.
He also must sit out the next postseason round. [MLB]
Can An Injured Player Return Two Rounds Later?
Potentially, yes.
For example:
- A player is replaced during the Division Series.
- He misses the remainder of the Division Series.
- He is also ineligible for the League Championship Series.
- If his team reaches the World Series, he can potentially be added again if healthy and eligible.
The automatic restriction created by the injury substitution covers the current round and the following round. [MLB]
Can Teams Add A Prospect For The Next Round?
Yes, provided the prospect is postseason-eligible.
A team could decide that a young pitcher, speed specialist or power hitter who was not on its Wild Card roster would be useful in the Division Series.
Because postseason rosters are submitted separately before each round, the club can add the player and remove somebody else from the previous roster without needing an injury justification. [MLB]
Can A Player Be On The Division Series Roster But Not The World Series Roster?
Yes.
Appearing in one round does not guarantee a player a roster spot in the next.
A team could use a pitcher during the Division Series, leave him off the League Championship Series roster and then potentially restore him for the World Series.
Those changes are allowed because every round has its own 26-man roster.
Do Players Who Are Removed Between Rounds Face A Waiting Period?
Not simply because they were left off the next roster.
The penalty involving the following round applies when a player is replaced during a series because of injury.
A healthy player who completes one round and is then omitted from the next round’s roster is not subject to that same injury-replacement restriction.
He could potentially be restored for a later round.
Example: How A Team Could Change Its Roster Through October
A hypothetical postseason team could construct its roster like this:
Wild Card Series
- 12 pitchers
- 14 position players
- Only three starting pitchers because the series lasts a maximum of three games
Division Series
- Add a fourth starter
- Remove a pinch-running specialist
- Carry 13 pitchers and 13 position players
League Championship Series
- Add a left-handed reliever to match the opponent’s lineup
- Remove a right-handed reliever
- Add a hitter who performs particularly well against left-handed pitching
World Series
- Restore a player who has recovered from injury
- Change bullpen composition again
- Add a defensive specialist based on the opponent
All of those changes can be permitted because a new roster is established before each round.
MLB Playoff Roster Rules At A Glance
- Postseason roster size: 26 players
- New roster before each round: Yes
- Can teams make changes between rounds? Yes
- Can a healthy player be added for a later round? Yes, if postseason-eligible
- Can a player be left off one round and return later? Yes
- Can teams freely change players during a series? No
- Can an injured player be replaced during a series? Yes, with MLB approval
- Injured pitcher replacement: Must be another pitcher
- Injured position-player replacement: Must be another position player
- Penalty for an injury replacement: Removed player misses the remainder of that round and the next round
- General postseason eligibility deadline: August 31
What’s The Simplest Way To Understand MLB Playoff Rosters?
Think of every postseason round as having its own roster.
A team chooses 26 players for the Wild Card Series. If it advances, it gets another opportunity to choose 26 for the Division Series. The process repeats before the League Championship Series and again before the World Series. [MLB]
The roster is largely locked once a series begins, with MLB-approved injury substitutions serving as the major exception.
So a player being left off a Wild Card roster does not necessarily mean his postseason is over. He could be added as soon as the next round if his team advances and determines that he fits its plans better for the next matchup.
