There are a thousand ways for a pitcher to experience enough pain and discomfort to keep him from throwing. For Brian Duensing, this time that means an intercostal strain. Let's talk about exactly what that is.
Intercostals are muscles found between the ribs. Excessive tension of these muscles can happen suddenly or over time due to an activity like pitching where the same movements happen over and over again. In pitchers it's a result of the repetitive motion and the twisting of the torso taking place. Apparently this type of injury tends to happen to the side of the body opposite of the throwing arm, with the pitcher experiencing a sharp pain in the chest or lower rib area. If the strain happened suddenly the pain will just appear, but over time it would have been a situation where Duensing could have continued to pitch for a time but he would have felt the pain after pitching.
How does the strain come about? There are a number of ways, and it's unlikely we'd get a totally transparent assessment of why. Possibilities include poor core stability, muscle weakness, improper warm-ups, excessive training, bad technique or mechanics, or simple wear and tear among other things.
Recovery time for an intercostal strain is two to three weeks for a Grade 1 strain, three to six weeks for a Grade 2, and perhaps three months in cases of a Grade 3 strain. For this reason it would surprise me if we saw Duensing before the middle of May at the earliest, including a minor league rehab stint, and it wouldn't surprise me if he was actually out until June.
Hopefully it's not anything serious and Duensing can get back on the mound in relatively short order. For now however, there are plenty of arms that deserve Major League innings and Caleb Thielbar is certainly one of them.