The A's will open up the season's second half against the Blue Jays on Friday with right-hander Daniel Mengden on the mound instead of lefty Rich Hill, who was scratched because of a blister.
It is not yet known when Hill will make his next start.
Mengden, who is 1-4 with a 4.54 ERA in six starts for Oakland, was likely going to start in Sunday's series finale before Hill's blister issue.
Hill is 9-3 with a 2.25 ERA in 13 starts this season.