MMA legend Francis Ngannou wrestled Andre Onana to the floor after Manchester United's win over Bodo/Glimt.
The Red Devils won 3-2 in the Europa League as Ruben Amorim made his Old Trafford bow.
But he was not the only man at the stadium for the first time as former UFC heavyweight champion Ngannou was in the stands.
He cheered on United goalkeeper Onana and after the game was spotted on the pitch talking to his fellow Cameroonian.
But Ngannou switched the ring for the pitch as the pair then began hilariously play-fighting.
It did not take the 19st 6lb man mountain long to grab Onana and tackle him to the floor.
There was a handshake between the two afterwards - but Onana has demanded a rematch.
He wrote: "I demand a rematch in a real ring! Let’s settle this once and for all!"
Fans won't want to see it though after fearing their No1 would get injured.
One joked: "Breaking news Andre Onana is out for the next decade with a broken everything."
Another added: "He is our only injury free player come on."
Ngannou spoke to TNT Sports post-match and said: "It was a good game, we had fun and there was a lot of action.
"Yes, it was my first time here, it was a good experience and we have a victory.
"Andre, he had a great game even though he takes a yellow card. He was the man of the game."
Ngannou watched the match from the stands and was sat alongside boxer Derek Chisora.
He is not the only MMA star to mingle with Premier League players on the pitch after a European game this term as Conor McGregor showed off his football skills then jokingly fought Bukayo Saka.