Between their 40-man roster and the disabled list, the New York Yankees currently have 45 players under major league contracts at the moment. While a number of those players can easily be dumped after the season, they also have many top prospects who will be eligible for the Rule 5 draft for the first time this winter and will need to be protected.
When the season ends, players on the 60-day disabled list need to be placed back on the 40-man roster, so the Yankees have 45 guys for 40 spots at the moment, even before considering the prospects that need to be added.