Sosnick declined to reveal the terms of Messenger's extension, but previous reports have said he could earn a total of $15 million -- which would place it among the largest deals ever signed by an American-born pitcher with an Asian professional team.
Messenger, 32, pitched in the major leagues with the Florida Marlins, San Francisco Giants and Seattle Mariners from 2005-09. He received interest from multiple MLB teams this winter before electing to return to Hanshin, where he's pitched since 2010.
Messenger, a 6-foot-6, 260-pound right-hander, has a 39-32 record and a 3.03 ERA in four seasons with Hanshin. He's struck out 519 batters in 623 1/3 innings with the Tigers.