When are MLB lineups released?
An MLB lineup only becomes official when the managers hand their lineup cards to the home plate umpire, about five minutes before the scheduled start. No league rule sets when a club must make its lineup public, and a posted lineup can still change.
The official moment: the lineup card exchange
The Official Baseball Rules (Rule 4.03, "Exchange of Lineup Cards") say that, unless the game has been postponed or delayed, the umpires go to home plate five minutes before the scheduled start and meet the two managers. The home manager hands over his batting order first, in duplicate, then the visiting manager does the same. The umpire-in-chief checks that the copies match and gives each manager a copy of the other team's order.
The rule is explicit that the umpire's handing over of the batting orders establishes them. After that, a team can only change its lineup through the normal substitution rules: a player who is replaced cannot come back into the game.
Under Rule 4.03(c), the lineup card should, as a courtesy, list each player's fielding position, and it must show which player is the designated hitter if one is used. Since 2022 both leagues use the designated hitter.
When teams make lineups public
Clubs make their lineups public before the card exchange through their own channels and the reporters who cover them. We are not aware of any league rule that sets a time for this, and we have not yet measured how far ahead lineups are posted. From the 2027 season we will log when each lineup is first posted and publish the distribution here.
Because there is no fixed time, the useful question for fans is not "when exactly" but "how settled is the lineup right now". That is what a start probability is meant to answer before the lineup is out.
Why a posted lineup can still change
Until the cards are exchanged, a posted lineup is a plan, not a rule. Common reasons for late changes include:
- a minor injury or illness discovered before the game (often reported as a "late scratch");
- a change of starting pitcher on the other side, which can change the planned matchups;
- weather, for example when a delayed start changes the plan for a doubleheader;
- a roster move, such as a call-up or a player going on the injured list.
What about the starting pitcher?
Clubs announce probable starting pitchers ahead of games, but those are announcements, not binding commitments, and they change. What is binding is the starter named on the lineup card; see how MLB probable pitchers work.
If a club wants to use an "opener", a reliever who starts the game for an inning or two, that pitcher is the starter on the card.
What this means for LineupMeter
- Before a lineup is posted, we show projections with a start probability for each player.
- Once a lineup is posted, we will show it as posted, and still flag that it is not official until the card exchange.
- For grading, we save our projections at fixed times before each game and compare them with the lineup that actually started. See our accuracy policy.
Sources: Official Baseball Rules, rules 4.03, 5.10 and 5.11. LineupMeter is not affiliated with MLB; see our disclaimer.