Man Utd fans are concerned after seeing what Francis Ngannou did on the Old Trafford pitch following Bodo/Glimt win

Manchester United fans were left baffled by what former UFC star Francis Ngannou was doing at Old Trafford on Thursday evening.

The Cameroon-born fighter was in attendance for Ruben Amorim’s first home game in charge of the Red Devils as they ran out 3-2 winners against Bodø/Glimt in the Europa League.

Ngannou recently returned to action himself, having pursued a career in boxing, losing to both Anthony Joshua and Tyson Fury before returning to the octagon with a first-round knock-out victory against Renan Ferreira in October of this year.

First, the MMA star posed for photographs with United's keeper Andre Onana.

But what followed was unexpected, to say the least.

The pair began shadowboxing on the Old Trafford pitch before Ngannou appeared to grab Onana, who attempted to evade his counterpart’s grip before the fighter dragged the Red Devils’ man to the floor.

Ngannou then mounted Onana and jokingly pretended to elbow and punch him while he was on the ground.

Of course, the pair were merely joking around, and both saw the funny side of the exchange.

Fans were quick to give their thoughts on social media.

One said: “Probably like a minuscule 5% chance for small injury with that takedown style. Francis knows what he’s doing.”

Another added: “That’s how you end up with Tom Heaton as your starter.”

With a third saying: “Please don’t injure my goalie”

While a fourth exclaimed: “Ban fighters from the ground immediately he could of been injured.”

A similar incident occurred at the Emirates Stadium after Arsenal’s 2-0 win over Paris Saint-Germain in the Champions League back in October.

On that occasion, UFC fighter Conor McGregor appeared to joke around with England star Bukayo Saka. The Irishman was involved in a pretend ‘sparring’ session with the Gunners man before the footballer told him to “be careful” before the MMA fighter shook his hand.

Saka took to Instagram shortly after, captioning a picture of the pair: "Good to meet you @thenotoriousmma. No harm done, just a friendly spar."

However, this incident did lead to concerns over player safety, with The Times revealing McGregor had not gained permission from Arsenal to enter the Emirates pitch.