Amidst the Stros’ free fall over the past month, the worst news to arise to date is All-Star pitcher Roy Oswalt‘s back injury that forced him to miss a start on Sunday afternoon against the Reds. Major League Baseball injury expert Will Carroll passes along the latest information on Oswalt’s back injury, which came on the heels of a pulled hamstring that Oswalt endured in his previous start:

There is no question in my mind that Roy Oswalt has a cascade injury. In the always-great Alyson Footerís article at MLB.com, Oswalt all but says so himself. ìI may have altered my mechanics,î he says, referring to what he did after straining his hamstring. Oswalt is now dealing with mid-back spasms, an unusual location. Elsewhere in the article, we get clues. Oswaltís back only acted up when he threw curves, meaning that his mechanics remained altered into this session. Mid-back spasms usually involve some muscles rather than structural problems, so this isnít as bad as it sounds. The Astros medical staff will have to stop the pain-spasm cycle, the Astros field staff will have to keep Oswalt from altering his mechanics, and Oswalt will have to listen. A decision on the DL wonít be made until mid-week and would follow an as-yet-unscheduled MRI.

The Stros have one of the best medical staffs in Major League Baseball, so Roy O’s injury will be handled conservatively. But make no doubt about it — this Stros club is barely a .500 team with Oswalt; the club is not close to being even a .500 club without him.