Rivera begins his first season with the Ducks and third in the Atlantic League. The right-hander spent four seasons at the Major League level with the Washington Nationals and one with the Arizona Diamondbacks. He made his big league debut on May 25, 2006 with Washington and earned a hold in an 8-5 win over the Houston Astros. The Puerto Rico native went on to finish that year with a perfect 3-0 record, a 3.43, one save and 41 strikeouts in 54 games. In 249 Major League games, he has a 13-15 record with a 4.29 ERA, four saves and 192 strikeouts.

The 36-year-old spent the 2012 season with the Sugar Land Skeeters in the Atlantic League. He compiled a 2-0 record with a 2.20 ERA and one save in 18 games. The year prior, the righty appeared in 28 games with the Road Warriors. He has spent time with six Major League organizations (Twins, Mets, Brewers, Expos/Nationals, Indians and Diamondbacks) throughout 14 seasons of professional baseball. In 432 minor league games (two starts), he is 38-31 with a 3.03 ERA, 87 saves and 605 strikeouts in 611 and one-third innings. Rivera was originally drafted by the Minnesota Twins in the ninth round of the 1998 amateur draft.