MMA fighters react to Conor McGregor's leg injury, loss to Dustin Poirier at UFC 264

Conor McGregor suffered a serious injury that brought his fight against Dustin Poirier to an immediate end at the conclusion of Round 1. Jeff Bottari/Zuffa LLC

The first round of the UFC 264 main event in Las Vegas on Saturday was eventful, with Dustin Poirier ultimately taking Conor McGregor to the ground as they exchanged strikes back and forth. But as the action moved back to the feet in the closing moments of Round 1, McGregor stepped backward and his foot landed awkwardly and resulted in an apparent serious leg injury to the Irish star.

McGregor was unable to stand up, and the doctors called an end to the fight, giving Poirier a TKO victory and a 2-1 edge in their series.

Many members of the UFC roster had instant reactions to McGregor's injury -- and Poirier's victory -- on social media.