Joe Mauer

UPDATE: La Velle Neal is suggesting that the Twins believe that Mauer will be able to get back into the lineup by next week, and should be in the lineup for opening day. This is great news (so long as it holds up), and indicates that the injury was closer to a bone bruise or bone sprain than anything more serious. Good job by Mauer of alerting the training staff immediately. For posterity sake, I'll leave the original post up so you can see my initial thoughts on this injury.

Original Post

La Velle E. Neal of the Star Tribune is reporting that Joe Mauer has been diagnosed with a "stress reaction" in his left fibula. He is set to be re-evaluated on Sunday, and will be treated with a bone stimulator and physical therapy. So, what exactly is a stress reaction, and what is the significance of the injury? Keep in mind that I'm no doctor, and that any information I have is sheer speculation aided by some light google research.

For starters, stress reactions are a kind of bone injury that fall somewhere between bone strains (which are usually non-painful) and stress fractures (which are quite painful). Untreated, stress reactions will develop into stress fractures. The most important method of treatment for someone with a stress reaction of the fibula would be to keep that person off of his leg to allow it time to heal. The fact that this injury was caught fairly early, before it developed into a stress fracture, is significant.

Every bone injury is different, so there is no way to know how long Mauer will miss while this heals. However, because of the nature of the injury, the Twins will need to be very careful and be certain that the injury has healed before they allow him to return to his catching duties. Something he's been doing has been putting undue strain on the fibula, resulting in the stress reaction. Typically, these kinds of leg injuries are the result of running on hard ground with insufficient padding in the shoes. However, I imagine there are a number of people out there who are wondering if catching could be partly to blame. If so, the cries of people like my friend Marty Andrade, who has been calling for Mauer to move to third base for some time, may be more likely to be heard.

So how long will Mauer miss? It's impossible to tell, really, but there are some possible indications available. Actual stress fractures can take anywhere from 4-12 weeks to heal properly, so I think it's safe to say that 6 weeks is an absolute outside bound for Mauer's injury, since he has the less severe stress reaction. At the worst, then, we could probably expect to see Mauer miss all of April, and possibly be asked to rehab for a week or so to get back in the groove before returning sometime in early May.

But could he be back sooner? That depends on how bad the injury really is. Once again, these kinds of injuries lie on a continuum between mere bone bruises or bone sprains, which typically heal relatively quickly and probably wouldn't keep a player out for more than a week, to the very serious stress fractures, which take up to 12 weeks to heal. If Mauer's injury is closer to a bone bruise or bone sprain, then we could be talking just 2 or 3 weeks that he'd be out.

Bottom Line: I expect Mauer to miss the start of the season, being out for at least the first two weeks. And frankly, I want the Twins to be as cautious with him as possible. Take a month if you have to, just get him healthy before he returns. And if smart people in white coats tell you that this was caused by squatting down to catch (which may or may not even be possible, so let's not jump the gun here) . . . consider buying him a third baseman's glove. It also means that Mike Redmond will be getting the bulk of the catching duties at the start of the season, and that Chris Heintz is very likely to make the big league club as Redmond's early season backup.