Conor McGregor: Max Holloway Is Not The Best Boxer In MMA, Iâll Prove It At UFC 257 Conor McGregor is determined to prove he, not Max Holloway, is the best boxer in MMA and insists he will do just that when he squares off against Dustin Poirier at UFC 257 this weekend. Holloway wowed fans and fighters with his performance against Calvin Kattar at UFC Fight Island 7. The former featherweight champ displayed his elite-level boxing skills to beat up Kattar over five rounds to claim a lopsided decision win. In the fifth and final round, âBlessedâ began talking to the commentators. He told Daniel Cormier, Dan Hardy, and Jon Anik he was the best boxer in MMA while simultaneously dodging punches from Kattar.