Coffman was rushed to the hospital Tuesday night after alerting team trainers of severe pain in his lower abdomen. The sophomore underwent the surgery early Wednesday morning and is expected to miss two to three weeks, Rams coach Jim McElwain said.
The 5-foot-10 Coffman had been working with Colorado State's first-team offense, but McElwain indicated that he won't play in the Sept. 1 opener against the rival Buffaloes.
"You have to plan without him," McElwain told reporters after Wednesday's practice. "I look it not as a deterrent, but actually it allows somebody to step up, grab the flag, take his reps on offense as well as in the return game. It gives somebody an opportunity to step up and be a player."
Coffman played in all 12 of Colorado State's games last season, finishing with 210 yards on eight catches for a team-best average of 26.2 yards per reception.