Brazilian grappling specialist Paulo Thiago (15-5 MMA, 5-5 UFC) has been forced out of a planned UFC Fight Night 27 contest with “The Ultimate Fighter 17” winner Kelvin Gastelum (6-0 MMA, 1-0 UFC).

Combate.com first reported the withdrawal, pinning the decision on a knee injury suffered this past week. UFC officials are now seeking a replacement opponent for Gastelum.

Featuring a headlining contest between Carlos Condit and Martin Kampmann, UFC Fight Night 27 takes place at Aug. 28 at Indianapolis’ Bankers Life Fieldhouse. The evening’s main card airs on FOX Sports 1 following preliminary bouts that air on FOX Sports 2 and stream on Facebook.

Picked last on “TUF 17,” Gastelum outwrestled and outworked four straight middleweight opponents to earn a spot in the tournament final at The Ultimate Fighter 17 Finale. There, he pulled off a major upset by outpointing show favorite Urijah Hall to win the reality show.

Prior to “TUF,” he racked up five straight wins with no losses on the regional circuit.

Thiago, meanwhile, saved his job with the UFC when he outpointed Michel Prazeres at UFC on FX 8. Prior to that, he went 1-4 in the promotion. To date, his most significant accomplishments are a pair of wins over American Kickboxing Academy fighters Josh Koscheck and Mike Swick.

A timetable for Thiago’s return wasn’t immediately established.

For more on UFC Fight Night 27, stay tuned to the UFC Rumors section of the site.

(Pictured: Paulo Thiago)