With September call-ups beginning just a couple of days ago, it’s a perfect time to reflect on how a few key rule changes completely redefined the strategic landscape of Major League Baseball. Before the significant rule changes of 2019 and 2020, the landscape of the second half of the season was a remarkably different, and often confusing, strategic environment. The July 31st trade deadline has always been widely covered but was not a definitive final day for player movement. Before MLB stopped allowing waiver trades in August teams were allowed to continue making trades for an entire month through a complex revocable waivers trade system.
This convoluted process created a prolonged, month-long negotiation period that served as a strategic safety for front offices to turn to when a player suffered a season ending injury after July 31st. The process allowed a struggling team looking to trade a player after July 31st to place him on waivers. If another team claimed him, the original club had the option to pull him back and keep him on their roster, effectively canceling the waiver and allowing them to gauge market interest without risk. This allowed front offices to adopt a wait-and-see mentality, holding onto assets until later in the season to see if a need arose.
This system was famously exploited when the Houston Astros acquired ace pitcher Justin Verlander from the Detroit Tigers just minutes before the August 31st deadline in 2017, a move that helped them win the World Series. Similarly, outfielder Andrew McCutchen was traded in August 2018 after clearing waivers, demonstrating how even valuable players could be moved after the initial deadline.
There is also the fact that prior to 2020 teams could expand their active roster from 25 to the full 40-man roster on September 1st. This practice was widely criticized for making games longer due to a constant parade of relief pitchers and pinch-hitters. The game in September was a fundamentally different sport than the streamlined, 25-man roster games of the postseason, creating a strategic and competitive imbalance.
The changes in 2019 and 2020 were very impactful. The more impactful one was the complete elimination of August trades for any player on a team’s 40-man roster. This established a single, definitive trade deadline on July 31st, making it the final opportunity for a team to acquire a player who could really thread the needle. While teams can still pick up players who were placed on outright waivers that is allowed before July 31st. Therefore, it the move may turn out to be less impactful for contenting teams.
The other major change, implemented in 2020, streamlined September rosters. Since 2020, teams have only been able to expand rosters to a maximum of 28 players on September 1st, with a new rule restricting the number of pitchers a team can carry to 14. This was a direct attempt to curb the issue of bullpen parades that plagued the old system.
The combination of a single deadline and streamlined rosters has fundamentally altered the need for front offices to make strategic moves both before and after the July 31st trade deadline. The elimination of the August waiver safety valve has placed a massive premium on decisiveness. Front offices can no longer afford to be indecisive or wait to see how their roster performs in August. A team must be brutally honest with itself by July 31st about whether they are a buyer or a seller, as there is no second chance to add a crucial piece.
This has made the July trade market more frantic and competitive. This year the new rules forced a perennial playoff contender like the Padres to be aggressive and acquire impact talent like they did with Mason Miller in July, as the opportunity to get a player of that caliber in August is no longer an option.
The new rules have also dramatically increased the value of a team’s internal organizational depth. In the past, a team suffering a key injury in August could often patch the hole by acquiring a veteran via waiver claims. In September teams are now limited to a 28-man roster instead of being able to use their entire 40-man roster causing them to rely mostly on their minor league system when filling unforeseen needs. This creates a direct link between the new rules and the imperative to build a deep, talented farm system, as a team’s ability to remain competitive is now tied to its ability to develop and have readily available talent on its 40-man roster.
Here’s the thing, folks: The new September roster rules have transformed call-ups from a broad rite of passage into a precise decision-making process. The old system, which allowed teams to bring up every player on their 40-man roster, was an opportunity to give players a cup of coffee. With only two additional spots now available, and a limit on pitchers, front offices must be far more selective. Teams now use these two high-value slots to address a very specific, late-season need, whether it’s a pinch-runner, a defensive replacement, or a specific bullpen arm.
With that… Eliminating August waiver trades and limiting teams to 3 September call-ups have reshaped the strategic landscape of the game, creating a more decisive and competitive game. The hard trade deadline has compelled front offices to be more proactive, replacing a wait-and-see mentality with a now-or-never approach. and the reduced September roster has made internal organizational depth a far more valuable asset. While teams can still pick up players on waivers after July 31st they must do so without making a trade. The strategic choices made by front offices today are no longer about exploiting a complex set of rules but about making the right call under a clear, unyielding set of constraints.