GODSMACK frontman Sully Erna has been forced to pull out of the Rock 'N' Roll Marathon after sustaining an unspecified injury. The event is scheduled to take place on November 11 in San Antonio, Texas.A post on GODSMACK's official web site reads as follows: "Unfortunately, because of an injury, Sully has chosen to back out of the San Antonio Marathon on Nov. 11. He plans on continuing his training as soon as he is feeling better and appreciates all the fan support thus far. Fortunately, there will be other marathons in the near future and he looks forward to participating in one of them. He may have to take a little break for now, but he WILL be back in action very soon!" The Rock 'N' Roll Marathon series is a collection of road running events owned and operated by Competitor Group, Inc. The series is known for lining race routes with live bands, cheerleaders and themed water stations. Rock 'N' Roll Marathon started as a single race in 1998, and is now said to be the "world's largest running series," with a global tour schedule of 27 events in 2012. GODSMACK recently scrapped a number of dates on its European tour due to Erna's vocal problems. The singer told The Pulse Of Radio that he's fine now, and explained what happened. "It was actually a bit of an infection that I had in the back of my throat, and I was exhausted, I hadn't slept in three days when we got to Europe, and it was just a combination of being like really tired, singing exhausted and just pushed myself a little too hard," he said. "And I injured it enough that I had to kind of shut it down, but it wasn't like a permanent injury or something like that. It was the first and only time it's ever happened in my career, and I don't expect this to become a habit." The European jaunt was GODSMACK's first in nine years, although they were only able to complete two of the fourteen shows, in London and Belgium.