McClellan is on the 15-day disabled list with a strained hip flexor, and said he should be ready to pitch Wednesday against the Nationals.
"I felt great," he said. "I didn't feel any discomfort, and I felt like I was well rested and my stuff was sharp. ... Yesterday was kind of like my game day -- a longer one -- and [Sunday] will be a light one, and then get ready for Wednesday."
McClellan, who is 6-2 with a 3.86 ERA this season, said Wednesday was the first time he didn't feel pain while pitching, and though he dubbed his return "a slow process," he said the swelling has mostly subsided.
On the other side of the clubhouse, outfielder Allen Craig's swollen right knee still won't allow him to play. Craig said he hoped to be able to return this series against the Brewers, but manager Tony La Russa said the team will have a decision to make in the coming days.
"I could walk around here fine, but that's not really being an athlete and going out there and playing a game," Craig said. "There's nothing structurally wrong with it, so it's just a matter of getting the swelling out. We're doing everything we can, icing it like 10 times a day, but I banged it pretty good. So it's going to take a little bit of time, but I don't think it's going to be much longer."