"This is the best he's felt, best action on the baseball and came away feeling good, so we'll make a decision on what we're going to do with him, whether it's going to be on rehab start to make sure we're past this, or put him in a game," A's manager Bob Melvin said.
Manaea, who has been on the disabled list with a shoulder strain since April 27, threw all of his pitches in the 38-pitch session Saturday.
"No pain, no soreness or anything like that," Manaea said, "and I felt like I was trying to go 100 percent and everything felt really, really good.