The highlight/lowlight came early this year with McGregor throwing a trolley dolly at a bus window during a media day in Brooklyn - Nurmagomedov was inside the bus. Furious UFC president Dana White said it was the "most disgusting thing...in the history of the company".
Days earlier, a McGregor teammate and Nurmagomedov argued in a hotel lobby. Nurmagomedov this week referred to McGregor as "some alcoholic guy" suggesting he used a lot of "drugs and whiskey".
Quotable quote:
"Conor is quite narcissistic, he cares about materialistic things and he wants more and more and more. Conor does his thing for marketing reasons." Fellow Irish fighter Myles Price, a former McGregor team mate, on his countryman's increasingly outrageous behaviour (USA today).
Who is Khabib "The Eagle" Nurmagomedov?
The 30-year-old is the first Russian and Muslim to hold a UFC title. He has a wrestling and judo background, and is undefeated in 26 fights with 10 knockouts. This is his first defence of the lightweight title.
Conor McGregor...back after nearly two year absence. Photo / Photosport
Conor "Notorious" McGregor is...
The most famous MMA fighter on the planet. The 30-year-old former plumber from Dublin has 21 wins from 24 fights, with all three losses by submission. His last appearance in a ring was against undefeated boxing legend Floyd Mayweather jr., at the T-Mobile arena in August last year. Mayweather won the boxing contest comfortably, as expected, but McGregor acquitted himself pretty well. McGregor's last MMA fight was in late 2016.
The tape: At 1.78m, Nurmagomedov is slightly taller than McGregor, but the Irishman has a 10cm reach advantage.
"I think he is a man with a glass chin that hasn't been cracked yet...devastating, devastating KO. I hope it's not too early, to be honest. I believe I will clatter him, he will crumble."