As a Rule 5 Draft pick, Blackley was offered back to the Giants, but San Francisco refused to pick up his contract. Rather than becoming a free agent, Blackley -- who also turned down the option to go to the Giants' Triple-A club in Fresno -- chose to return to the Phillies.
The Phillies have to make a decision on three other players.
Outfielder Chris Snelling is out of Minor League options, so he will have to clear waivers before he can be sent to Triple-A Lehigh Valley. Snelling could benefit from the Phils carrying 11 pitchers, but he would be in jeopardy when closer Brad Lidge returns, potentially on April 5.
The team has been trying to trade third baseman Wes Helms and might be able to in the next few days before rosters are finalized on Sunday. If Helms is not traded, it is a strong possibility that he'll be released.
It also appears that infielder Ray Olmedo will not make the Phillies out of camp.
Chris Girandola is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.