Tyson Fury was in attendance at Old Trafford as Manchester United played Manchester City on Saturday afternoon.
Fury, a United fan, shared his excitement ahead of the game.
Posting a video on social media, Fury said: "Come on the Reds! We're off to the derby! Come on the Reds!"
However, he came away from the game disappointed as United were beaten by their fierce rivals.
Goals from Eric Bailly (own-goal) and Bernardo Silva gave City a 2-0 victory.
Fury was so upset that he took to social media to call out United's players after the game.
He started: "After today's defeat from City with Manchester United, it is fair to say that United are taking a worse beating than Deontay Wilder took in all his fights versus me.
"We are absolutely getting smashed out there.
"I think partly it is because the players - with no disrespect to any of you - it doesn't seem like you are digging deep to try and win these games.
"It just seems like you're happy to get through them and whatever happens, happens.
"You know, when I fought Wilder and I was on the floor, and any man I've ever fought, I never believed I was going to lose the fight.
"I always believed I would come back and win, and that is called a winner's mentality, something that you guys in the last two games have just not had.
"I think me and Patrice Evra will come down to training and give you the hard word of what you need."
Whether Fury actually does go to the training ground to speak to Ole Gunnar Solskjaer and his players remains to be seen.
Given his experience in boxing and everything he's been through, there's no doubt that he can teach United's players a thing or two.
View some reaction to the video below...
United now have two weeks until their next game, where they travel to Vicarage Road to take on Claudio Ranieri's Watford.
They are already nine points behind league leaders Chelsea and desperately need to get back to winning ways.