Dunn entered camp 10 pounds lighter than last season, Ryan Divish of The Seattle Times reports.
Dunn made several improvements during the offseason, including an increased fastball velocity that he displayed during his first bullpen session Friday while striking out Kyle Seager, Evan White and J.P. Crawford. The right-hander also altered the grip on his changeup and shed some pounds. Manager Scott Servais said that his weight loss could help him "move down the mound better and hopefully improve his stuff." Dunn made 10 starts for the Mariners last year but isn't guaranteed a spot in the team's six-man rotation to begin the season.