On March 5, 2013, while hitting off a tee during practice at the World Baseball Classic, first baseman Mark Teixeira injured his right wrist. He throws right-handed and bats from both sides, so this is a serious injury that will side-line him about two months. He strained one or more of his tendons. The most common one strained while batting is the wrist tendon that moves the hand upward and toward the pinky side side of the forearm. The anatomy includes not only the extensor carpi ulnaris tendon (ECU), but also the subsheath, the ligament that holds the tendon against the ulna head, the knobby bone on the outside of the wrist. The ECU subsheath acts like a beltloop holding the tendon, or belt, in place. It usually tears in full, forceful supination, the palm up position at the end of the swing in the right hand, when batting lefty. Treatment includes 4-6 weeks of splinting, or surgery in symptomatic complete tears. Rehabilitation includes sport-specific exercises.