WSOF president Ray Sefo confirmed the news to ESPN.com on Wednesday, after an earlier report by MMAFighting.com. Fitch is likely to receive a new opponent.
"[Shields] injured his shoulder and called us a couple of days ago," Sefo said. "I think, roughly, he said he'll be out about six weeks or so. Then he would start camp right after that. He probably won't fight for another four or five months."
Shields (29-7-1) signed a deal with WSOF earlier this year, after he was released by the UFC following a 4-3 run in the Octagon. He lost a unanimous decision to Hector Lombard at UFC 171 on March 15.
Fitch (25-6-1) is 1-1 since signing with WSOF last year. He was originally scheduled to fight Rousimar Palhares for the promotion's 170-pound title July 5, but Palhares withdrew due to personal reasons.