The team released Mathieson on Tuesday to allow him to pursue an opportunity to pitch with a professional team in Asia.
Mathieson, 27, went 1-4 with a 6.75 ERA in 15 games in three seasons (2006, 2010-11) with the Phillies. He went 32-37 with a 3.75 ERA and 34 saves in 200 games in the Minor Leagues. He had three different surgeries on his right elbow, including two Tommy John ligament replacement surgeries, but still came back to pitch again in the big leagues.
The Phillies selected Mathieson in the 17th round of the 2002 First-Year Player Draft.
The moves leaves the Phillies with 39 players on their 40-man roster.
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.