Note: As part of MLB's health and safety protocols during the COVID-19 pandemic, each club will have a 30-man roster for the first two weeks of the 2020 season, 28 for the next two weeks, and 26 for the remainder of the season. Teams will submit 60-man pools -- that is, the group of players who will be able to play for them this season. According to the league's Operating Manual, all players on a 40-man roster "that the club anticipates participating" during the season will be part of the player pool, while the rest will be made up of non-40-man roster players under contract. Each team will be permitted a three-player taxi squad for every road trip, giving them immediate options to replace an injured or COVID-19 infected player. There will be no limit on the number of pitchers on the active roster, or on position players pitching. Rather than a 10-day injured list for position players and 15-day injured list for pitchers, there will be a 10-day injured list for all players in the shortened season. The 60-day injured list will be reduced to 45 days. The 7-day injured list will be unaffected. There will also be a COVID-19 injured list with no minimum or maximum number of days per trip.
In a typical season, the 15-day injured list allows clubs to remove injured pitchers or two-way players (position players who are eligible to pitch in any circumstance) from the 26-man roster (it was 25, prior to 2020) while keeping them on the 40-man roster. Pitchers or two-way players can be placed on the 15-day injured list for any type of injury, and must remain out of action for at least 15 days, though the player can also stay on the list for considerably longer than 15 days, if necessary.
Players may be placed on the 15-day injured list "retroactively," meaning the stint is backdated to the day after the last date on which the player appeared in a game. For instance, if a pitcher was removed from a start due to shoulder pain on June 1, he could be placed on the 15-day injured list on June 3, retroactive to June 2. In that case, he would be eligible to return from the injured list on June 17.
The injured list used to be 15 days for all players until the 2017 season, when it was reduced to 10 days. Position players will still have a 10-day IL under the new rules.