One of the most heavily anticipated matchups in the UFC’s lightweight division has been scrapped. Khabib Nurmagomedov (22-0 MMA, 6-0 UFC) will not be competing at UFC 187.

MMAjunkie today learned from a person close to the fighter that an injury has forced the undefeated standout to withdraw from a planned matchup with Donald Cerrone (27-6 MMA, 14-3 UFC). The person spoke on the condition of anonymity because they are not authorized to publicly discuss such matters.

While the exact nature of the injury wasn’t immediately revealed, additional sources indicated Nurmagomedov’s knee was the culprit. An exact timetable for his return wasn’t established.

Nurmagomedov’s management team wasn’t immediately available for comment when contacted by MMAjunkie.

Meanwhile, the sources indicated UFC officials are currently searching for a replacement opponent for Cerrone for the May 23 event in Las Vegas.

Just this past week, Nurmagomedov told MMAjunkie that he was back at “100 percent” and ready to challenge for the UFC lightweight belt later this year. The winner of the Cerrone vs. Nurmagomedov bout was expected to earn a booking with current champ Rafael dos Anjos. However, with Nurmagomedov now out of the fight, the UFC’s lightweight title picture is just a little less clear.

For the latest on UFC 187, check out the UFC Rumors section of the site.