Blue Jays third baseman Josh Donaldson will officially begin his rehab assignment with Class A-Advanced Dunedin, according to Bob Nightengale of USA Today. The Major League Baseball deadline to trade for a player and have him be eligible for the postseason is 11:59 p.m. ET on Friday. 

Donaldson has only played 36 games this season and has been on the disabled list since June 1 with a strained left calf muscle. His timetable for a return has been somewhat of a mystery since being placed on the 60-day DL. Earlier this month, a Blue Jays spokesman said that Donaldson was "ramping up intensity in Florida over the next several days."

Donaldson's tenure with Toronto could be nearing its end, with the possibility of the Blue Jays flipping his $23 million salary to a postseason contender increasing, if he shows significant progress over the next few days. His locker was notably cleared out on Sunday at Rogers Centre, per TSN's Scott Mitchell. 

"I want to play soon and wanted to make sure I have everything I need to do that," Donaldson said in the statement, which was issued through a club official. "So I asked the staff to pack my locker, then I can go through it."

The 32-year-old has struggled when healthy this season, batting .234 with five home runs and 16 RBI in 137 at-bats.