A native of Surrey, British Columbia, Loewen hit .227 with eight home runs and 26 RBIs last year with the New York Mets' Triple-A team at Buffalo.
Loewen spent the 2009-11 seasons in the Blue Jays organization after converting from a pitcher to a position player. He hit .306 with 17 homers and 85 RBIs at Triple-A Las Vegas in 2011. He was 6 for 32 (.188) with one homer and four RBIs for Toronto during a callup in September 2011.
The 26-year-old Rasmus hit .223 last year, when he set career bests with 23 homers and 75 RBIs. He has a .243 average with 76 homers and 246 RBIs in four big league seasons with St. Louis and the Blue Jays, who acquired him in July 2011.
Rasmus made $2.7 million last year.