Lightweight champion Khabib Nurmagomedov announced his retirement following his second-round win over Justin Gaethje at UFC 254 on Saturday.
Khabib's father and head coach Abdulmanap Nurmagomedov died in July because of complications with the coronavirus, and the Russian champion said his father's death played a role in his decision to leave the sport.
"This was my last fight," Khabib Nurmagomedov said. "No way am I going to come here without my father. ... I promised [my mother] it will be my last fight. If I give my word, I have to follow this."
Coming into Saturday's event, Gaethje was the interim lightweight champion after his knockout of Tony Ferguson in UFC 249. The American stepped in for Nurmagomedov after the reigning champion was unable to travel from Russia due to COVID-19 travel restrictions.
Nurmagomedov submitted Gaethje in the second round, retiring with an undefeated record of 29-0.
The Russian has held onto the lightweight title since April 2018, when he defeated Al Iaquinta at UFC 223. He then retained the title after beating Conor McGregor at UFC 229 interim champion Dustin Poirier at UFC 242.
McGregor, his old rival, reacted to the news on Twitter: “Good performance Khabib. I will carry on. Respect and condolences on your father again also. To you and family. Yours sincerely, The McGregors.”