Chiesa out of Ferguson fight at UFC Fight Night 91

Back issues will force Michael Chiesa out of his main-event bout opposite Tony Ferguson at UFC Fight Night 91.

UFC officials confirmed the withdrawal to John Morgan of MMAjunkie.

A former "Ultimate Fighter" winner, Chiesa cracked the lightweight top 10 for the first time with a submission win over Beneil Dariush this past April. He was rewarded with a bout against the No. 3-ranked Ferguson at the UFC's Sioux Falls, S.D. debut on July 13.

Chiesa tweeted out a statement addressing the injury Monday.

The UFC is searching for a new opponent for Ferguson, who is coming back from a six-month layoff due to complications with his lungs. The former "TUF" winner has won his last seven fights.