In the wake of granting free agency to infielders Neil Walker and Martin Prado, along with Marlins outfielder Curtis Granderson, four were activated from the 60-day injured list.
After Prado, Walker, and Granderson were freed, the 40-man roster sat at 32. Starlin Castro was then also freed up when the Marlins declined to exercise his option.
The free agent signing period begins at the conclusion of the World Series, won three days ago by the Washington Nationals. According to Joe Noga, at Cleveland.com:
The conclusion of the fall classic starts the clock on a five-day “quiet period” where teams can negotiate exclusively with their own free agents, but are prohibited from signing anybody.