WWE sent out the following:

Roman Reigns undergoes emergency surgery

NASHVILLE, Tenn. — WWE.com has learned that Roman Reigns has undergone emergency surgery for an incarcerated hernia. Reigns had been in Nashville to promote tomorrow’s Night of Champions pay-per-view. His recovery time will be evaluated by the local surgeon and WWE physician Dr. Chris Amann, but he will be unable to compete against Seth Rollins tomorrow night. Check back with WWE.com for further updates on Reigns’ condition.