The 32-year-old never pitched for Bakersfield, but he threw some bullpen sessions in Seattle to keep his arm strong over the 11 days between starts.
Happ, acquired from the Blue Jays in a December trade for outfielder Michael Saunders, is 4-5 with a 4.14 ERA in 17 starts. He took a no-decision in his last outing on July 8 against the Tigers, allowing seven hits and four runs while throwing 103 pitches in four innings.
After going 3-1 with a 3.29 ERA in his first six starts, Happ has been credited with just one victory in 11 starts since May 9.