Janssen was released by the Red Sox on Sunday, Mark Polishuk of MLBTradeRumors.com reports.
Janssen exercised his right to opt out of his minor league deal with Boston, and will look to join a major league roster somewhere else. He has not yet appeared in the majors this season, but has pitched decently in the minors, posting a 2.87 ERA over 15.2 innings combined at the Low-A and Triple-A levels.