Brek Shea seemed likely to make the United States Gold Cup roster, but when Jurgen Klinsmann released his 23-man tea, Shea wasn't on it. But now we know why.

Shea has been dealing with a groin injury and isn't even close to full strength, he told the Orlando Sentinel.

"It just consistently got worse," said Shea. "I’ve been playing and running at 70 percent, not even. So I wanted to do something and not have it become a serious, season-long type of injury. … Hopefully whatever we do can sort it out. I’ve had this injury before, and if you don’t take care of it, it can last a long time."

Observers' opinions on Shea have been mixed. While he's certainly playing better now than he did in the last two years, when he was glued to the Stoke City bench, the American still isn't near the level that made him an MLS MVP candidate with FC Dallas. Klinsmann's experiment in moving him to left back has had its ups and down, but the manager has stuck with him and clearly liked what he brought to the attack from the fullback position.

Regardless of whether you like Shea and think he should have been on the Gold Cup, Klinsmann certainly does and it's likely that he would have been on the roster if he was healthy. But he's not, and now why know why he missed out.

Shea will sit for the next 10 days before being reevaluated, but that does open the door for him to be added to the U.S. team after the group stage. The rules allow for up to six players to be removed from the roster and replaced prior to the knockout stages. If Shea is cleared in 10 days and gets a match or two under his belt, he may be ready to go for the knockout stages and Klinsmann could call him in then.