Baez spent the past three seasons in Baltimore, but didn't pitch in 2008 after undergoing elbow surgery during spring training and missing the entire season. Baez returned to form last season, posting a 4.02 ERA in 59 games with the Orioles.
The terms of the deal weren't announced, but Baez last deal averaged $6.3 million per season for three seasons. His deal with Philadelphia is thought to be more in the neighborhood of $3 million per season and is contingent on Baez passing a physical.
Baez' signing signals the end of Chan Ho Park's run with the Phillies. Park and the Phillies were unable to reach an agreement on either the money or length of a deal.