"It was a battle to get him out of the game," manager Manny Acta said. "He's a fighter. He wanted to keep playing, but that's not smart to keep him out there and maybe make it worse.
"He's going to be shut down for a few days. He's not going to be able to swing the bat for a few days."
Choo had an MRI on Saturday, which revealed a strained muscle in his left side. He was kept out of the starting lineup Wednesday and Friday with what the team diagnosed "lower left trunk soreness." He entered Friday's contest in the eighth inning as a defensive replacement.
Choo said he felt no ill effects after taking batting practice Friday and Saturday. The 29-year-old first felt pain during an eighth-inning at-bat in the second game of Tuesday's doubleheader.
He said he only felt pain when he didn't swing the bat. When he took a full cut, he felt fine. But when he started his momentum forward and then stopped to take a pitch, he noticed the pain.
"Swinging is no problem," Choo said. "But even in soft toss, if I take a pitch, I feel it."