Zambrano has been without a team since finishing the 2012 season with the Miami Marlins. He made 35 appearances, including 20 starts, for the Phillies' National League East rivals last season. The right-hander went 7-10 with a 4.49 ERA and 1.50 WHIP.
Before his stint with the Marlins, Zambrano had spent his entire career with the Chicago Cubs. Starting in 2002, he posted nine straight seasons with an ERA below 4.00. His temper often overshadowed his talent, however, which might help explain why he was only able to fetch a minor league contract.
The Phillies are searching for rotation depth after a shoulder injury put former ace Roy Halladay on the shelf. They are also without offseason addition John Lannan, who struggled in three starts before going on the disabled list with a knee issue.
Cole Hamels, Cliff Lee and Kyle Kendrick are anchoring the staff in the meantime. Jonathan Pettibone has been impressive in his first five outings, going 3-0 with a 3.41 ERA. Even with his contributions, the club is short in the starting pitching department.
Only time will tell if Zambrano is capable of filling that void. His numbers over the past two seasons, high ERA and a declining strikeout rate, would suggest it's a long shot. But the Phillies clearly believed he was worth taking a chance on.
If he can return to his prior form, he would be a nice addition for the back end of the team's rotation. Philadelphia faces an uphill battle with the Atlanta Braves and Washington Nationals in the division. Their margin for error is already shrinking, so a move was necessary.
Plans for what the team expects to do with Zambrano in terms of getting him ready for major league action were not immediately announced.