One is a bone-crunching, brash UFC titan, the other a level-headed Scottish full-back.
Yet the unlikely bromance between Conor McGregor and Kieran Tierney continues to grow after "The Notorious" was asked his favourite footballer on Thursday.
There was only going to be one answer and the likes of Lionel Messi didn't get a look-in.
"He rose up and is a phenomenal, phenomenal football player," the Irishman gushed about the Arensal left-back.
"I am in conversation with him a lot. He is a great guy, a good kid and I'm rooting for him."
Tierney replied to "The King" with a Twitter message, saying: "Thank you so much brother! An icon and my hero. Learned so much from you."
The 22-year-old, who left Celtic for Arsenal in a £25m move this summer, previously credited training tips from McGregor for aiding his recovery from a groin injury earlier this year.
The pair cemented their mutual appreciation when they met for the first time at a UFC fight in Belfast in 2017.
And McGregor, who waxed lyrical about Tierney while in Moscow this week to announce his return to UFC seven months after retiring, was pictured in January 2018 wearing one of several signed Celtic tops sent to him by the Scotland international.