X-rays came back negative, though the Cardinals still chose not to start Craig in Wednesday's game against the Giants.
"I've been working through it, but I woke up today and it was pretty sore," Craig said. "I hit the concrete pretty hard in Cincinnati and it's been a little sore here and there. Today was the worst of it, unfortunately. That's how things go."
The discomfort is related to a collision Craig had with the railing along the first-base line while pursuing a foul ball in a July series at Great American Ball Park. Craig hardly slowed as he neared the tarp, and, while trying to make the catch, he hit his chest on the top of the railing as he fell toward the stands.
Afterward, he described the impact.
"I thought I had a bead on it and then the wind took it," Craig said that night. "It didn't feel good."
Both Craig and general manager John Mozeliak cautioned against panic, both expressing optimism that Craig would be in the starting lineup Thursday. Craig was available to pinch-hit Wednesday, though the Cardinals did not use him in their 15-0 loss to the Giants.
Craig, who has been diagnosed with a bone bruise, could not pinpoint why the discomfort increased so much Wednesday.
"I wish I had a better answer for you guys," he said. "Sometimes you wake up and you just don't feel good for some reason."
With Lance Berkman on the disabled list, Craig has taken over as the team's regular first baseman. He hit a pair of home runs in Tuesday's loss and is batting .298 with 17 homers and 58 RBIs in 69 games. Two unrelated injuries landed Craig on the disabled list earlier in the season.