Gregerson is sidelined with what is being considered a mild oblique injury, Joe Trezza of MLB.com reports.

The veteran reliever was scheduled to pitch Tuesday but didn't, and the reason why finally emerged. Gregerson did undergo an MRI and no one in the Cardinals' organization seems to be overly concerned about the issue, even though oblique injuries can keep players out for as long as a month in some cases if they are not treated properly. Regardless, this will put him behind schedule compared to the rest of the pitchers in camp.