September 1 is a milestone–and not just because my gym membership runs out that day.
By September 1, MLB rosters freeze in anticipation of the postseason–trades and call-ups from the minor leagues halt, and major league rosters expand from 25 men to 40 men.
This roster expansion, often referred to as the “September call-up” period, is meant to allow teams seeking postseason runs to load up their teams with young talent and extra depth. In case of postseason injury, for example, a minor leaguer on the 40-man-roster may be added to the 25-man roster and could be eligible to play anywhere from one inning to the entire rest of the postseason, because up to 40 men can suit up to play. Major League Baseball can accomplish this drastic roster growth each season because, unlike other professional sports leagues, there is no salary cap in the MLB–only a limit on the number of players eligible on the active roster at any given time.
The 40-man roster period is often the culmination of a volatile month in many players’ seasons, where clubs are hasty to trade, call up and send down players seemingly on a whim. If a team needs an extra arm to rest a fatigued rotation, a secondary infielder from their farm system or still wants to claim a player off waivers, players can be uprooted multiple times before the Sept. 1 deadline.
From a strategic standpoint, this complex trade/roster system makes crafting a roster for an MLB team both uniquely exciting and challenging. Even post trade-deadline, player movement is not only possible but highly probably–just ask Curtis Granderson, who was claimed off waivers and headed to the Dodgers just last week. Minor leaguers are perhaps the most frequently uprooted–for example, Yankees’ starting pitcher Jordan Montgomery, who was sent down to Triple-A in mid-August in order to clear a roster spot for CC Sabathia, will again return to the Yankees as a member of the 40-man roster on September 1.
So while the unique MLB roster expansion is fascinating, it makes for some of the most volatile Septembers for minor leaguers.
However, it can also make for the most exciting career debuts–because many professional careers begin on the postseason 40-man roster. Just another reason to be excited for September/October baseball.