Cain hasn't started in 10 days after being hurt on May 21, when he felt a twinge in his leg on his last pitch of the third inning.
The pitcher felt good after a bullpen session Wednesday and the team expects Cain to be fine for Saturday's game against the St. Louis Cardinals, barring any setbacks.
"He's fine, no issues there," manager Bruce Bochy told reporters.
Cain is 1-3 with a 3.66 ERA in eight starts this season.
The Associated Press contributed to this report.