Bettis, who entered the game with a 5-4 record and 4.91 ERA, allowed his ninth homer of the season to catcher Austin Hedges in the third, but kept his composure until the sixth inning. Bettis walked two straight batters and then allowed a two-run double to Matt Kemp with two outs to give the Padres a 3-1 lead.
Manager Walt Weiss and Bettis agreed that fatigue got the best of the pitcher.
"He started throwing balls in the middle of the plate that inning and that is usually a sign that there is some fatigue setting in," Weiss said.