Shane Carwin heard a sound no MMA fighter ever wants to hear.

Carwin, who can currently be seen coaching on The Ultimate Fighter, is expected to face Roy Nelson this December.

However, a slip during a recent practice session nearly ended that fight months before it ever goes down.

“It happened during wrestling. A guy was in on a single and I went to throw my hips back and I heard, ‘Pop! Pop! Pop!'” said Carwin, during a recent appearance on TapouT Radio. “So we stopped and he had to help me up. It’s down in size now. It was about the size of a watermelon, but now it’s the size of a cantaloupe.”

Carwin and Nelson are slated to square off December 15. Carwin, a former interim UFC heavyweight champion, was told he won’t need surgery and added, “we’re still going to push to stay in that fight.”

Photo credit: Esther Lin/AOL