Roster space is finite, so teams are constantly adding and removing players depending on their needs, their opponents and health.
The moves can be confusing for even the most intense fans, so Sportsnet has assembled this primer to help you track all of the action and what it means.
With regards to in-season roster moves, we’ve divided the moves into three categories for the sake of clarity:
REMOVING PLAYERS FROM THE ROSTER
Designated for assignment:
When you hear this, think ‘to be determined.’ Teams designate players when they need to clear a roster spot and want to pass a player through waivers or buy themselves some time.
A DFA always opens up a spot on the 40-man roster. In cases where the designated player is coming off of the active roster, the move creates 25-man space as well.
Once teams designate players, they have 10 days to determine their next step. Teams have three options: they can trade the player, release him or assign him to the minor leagues.
In nearly all cases, designated players must clear irrevocable outright waivers before being sent to the minor leagues.
In other words, 29 rival teams will have the chance to claim them.
Quick tip: DFA = TBD.
Recent Blue Jays example: The Blue Jays designating Dave Bush for assignment.
Teams place players on outright waivers to send them through waivers to the minor leagues. Outrighted players can be claimed, with the claiming team assuming the player’s salary.
Specific rules govern outright assignments, which often follow a DFA. For example, players must accept their first outright assignments unless they have three years of MLB service time.
If a player has a prior outright, however, he can reject the assignment and become a free agent. If he accepts the assignment, he's eligible for free agency at the end of the season unless he has been added back to the 40-man roster.
Quick tip: Teams outright players to move them through waivers to the minors or off the roster.
Recent Blue Jays examples: The Blue Jays outrighted Aaron Laffey and Shawn Hill off of the 40-man roster at the end of the 2012 season. Adam Lind was placed on outright waivers last year, but he was not claimed.
Once a player has been placed on his team's 40-man roster, the option clock starts. At that point, the team can demote and recall the player over the course of three separate seasons (or option years), without exposing him to other teams.
There's no limit to the number of times teams can option and recall players in the course of an option year.
Teams don't use options on players who spend full seasons at the MLB level. In fact, a player must spend at least 20 days in the minor leagues for the option to take effect.
Some players get four option years, but such cases are rare. Out of options players must clear waivers before going to the minor leagues.
Players with at least five years of service time can't be optioned without their consent.
Quick tip: Teams create 25-man roster space by optioning players to the minors.
Recent Blue Jays examples: The Blue Jays optioned Ricky Romero to the minor leagues at the end of spring training. Jeremy Jeffress was out of options, however, so the team designated him for assignment.
Disabled list - Teams can and do use the disabled list to create roster space. Placing a player on the 15-day DL opens up a 25-man roster spot, and placing a player on the 60-day DL opens up a 25-man roster spot and a 40-man roster spot.
Players sometimes go on the disabled list with dubious injuries. In some cases, the teams are placing reasonably healthy players on the DL for the purposes of roster management.
Quick tip: Teams use the DL to create roster space.
Recent Blue Jays example: The Blue Jays recently moved Dustin McGowan from the 15-day DL to the 60-day DL in a move that opened up a 40-man roster spot.
Release: There’s nothing more final than a release. Once a player is released he becomes a free agent and can sign with any team.
Quick tip: Released players immediately become free agents.
Recent Blue Jays example: The Blue Jays released David Cooper.
ADDING PLAYERS TO THE ROSTER
Major league contract:
Major league contracts require teams to place players on their rosters, in all cases the 40-man (Adeiny Hechavarria when he signed with the Blue Jays for example), and in most cases the 25-man.
High-profile free agents nearly always obtain major league deals, forcing teams to open roster space for their new acquisitions.
Quick tip: Major league contracts require MLB roster space.
Recent Blue Jays example: The Blue Jays signed Melky Cabrera to a major league deal last off-season.
Teams recall players who are already on their 40-man rosters. This move affects only the 25-man roster.
Quick tip: Teams recall players to the MLB level when they’re already on the 40-man roster.
Recent Blue Jays example: The Blue Jays recalled Travis Snider from the minor leagues multiple times before trading him to the Pittsburgh Pirates.
Minor league contract:
Minor league contracts do not require teams to free up roster space at the MLB level. The deals give teams the rights to players without creating a roster crunch.
Players sign minor league deals when they have limited leverage, often toward the end of their careers. Teams generally sign a couple dozen free agents to minor league contracts with invitations to spring training during the off-season.
Experienced players often have opt-out clauses in their minor league contracts. In fact, Article XX(B) of baseball's collective bargaining agreement ensures that certain minor league free agents with at least six years of service time must be added to the active roster, granted free agency, or paid $100,000 at the end of spring training every year.
Quick tip: Minor league deals don’t require space on the MLB roster.
Recent Blue Jays example: The Blue Jays signed Dave Bush to a minor league deal in December 2012.
A team selects the contract of a player to add him to the 40-man roster (and, in many cases, the active roster). If a team wants to add a player on a minor league contract to the MLB roster, it must select the player’s contract.
Every off-season teams need to select the contracts of certain players or risk exposing them to other clubs in the annual Rule 5 Draft.
Quick tip: Teams select players’ contracts to add them to the roster.
Recent Blue Jays example: The Blue Jays selected the contract of Dave Bush from triple-A Buffalo before he made his return to Toronto.