Sweeney has 73 games of Major League experience with the Seattle Mariners and the San Diego Padres. He has a Major League career record of 4-2 with a 3.38 ERA in 117 innings pitched. He pitched for the Mariners last season, where he appeared in 24 games at the Major League level and finished with a 3.16 ERA.

Sweeney also has seven seasons of Triple-A experience and a minor league career record of 69-49, a 4.04 ERA, and 855 strikeouts in 1,075 innings pitched in 283 games.

He also has three seasons of experience in Japan, playing for Nippon from 2007-2009. Sweeney joined the Patriots in Spring Training in 2010, but was signed by the Mariners when camp began.