From the official site:

The link between the Yankees' Shelley Duncan and his brother, Cardinals outfielder Chris Duncan, took a bizarre twist this week. Both players were diagnosed with hernias that figure to put their playing time in jeopardy.

Shelley Duncan, a 27-year-old who made an immediate impact with an initial power barrage, had an MRI exam administered on Wednesday at the Columbia Presbyterian Medical Center in New York, where Yankees team physician Dr. Stuart Hershon and Dr. George Todd diagnosed the rookie as having a bone bruise on his left pelvis and a small inguinal hernia.

Yankees manager Joe Torre said he was told that the hernia will not immediately require surgery, if at all, and Duncan was expected to fly back to Toronto on Wednesday.