who can be traded after the trade deadline
Major League Baseball transactions Teams may trade only players currently under contract. From the end of the previous World Series through July, trades between two or more major league teams may freely occur at any time. In August, trades may only be made after all players in the trade clear waivers or are not on 40-man rosters. Players acquired after August 31 are ineligible for the postseason roster unless they replace an injured player. Unlike in the NFL, NHL, MLS, and the NBA, teams may not trade draft choices (with the exception of competitive balance draft selections, which can be traded as explained below), but may purchase the rights to Rule 5 Draft Picks.[3]