Tyler Seguin's injury appears to be worse than it initially appeared.

Seguin underwent an MRI in Dallas on Friday which revealed a hairline fracture in his heel, according to Stars general manager Jim Nill.

Nill said in a statement that the 24-year-old Seguin suffered the injury in Canada's exhibition opener against the United States on Sept. 9.

It's believed Seguin was hurt when he tumbled feet-first into the end-boards. He briefly left that game, a 4-2 loss, but returned and even played the next night, also against Team USA.

Seguin evidently kept the severity of the injury hidden until it became too much to ignore. He withdrew from Canada on Tuesday, replaced on the roster by Buffalo Sabres centre Ryan O'Reilly.

Nill said Seguin's status for training camp would be re-evaluated in a week.

Stars captain Jamie Benn was also forced to withdraw from the tournament because of injury.