Roy Keane suggested that Manchester United looked "like a bunch of strangers" during their late FA Cup victory over Leicester City on Friday. 

Harry Maguire netted a controversial 93rd minute winner, planting Bruno Fernandes' free-kick beyond Mads Hermansen from an offside position, with the goal allowed to stand due to VAR not being in operation. 

Bobby De Cordova-Reid had given the Foxes the lead in the first half only for substitute Joshua Zirkzee to level the scores at Old Trafford in the 68th minute. 

United had to wait until the 65th minute to register their first shot on target, with Alejandro Garnacho seeing his effort cleared off the line by Caleb Okoli. 

Friday's win saw the Red Devils stay unbeaten in their last 19 home matches in the FA Cup, winning 17 of those (D2), but Keane was quick to look at the deeper issues. 

Indeed, United have now shipped 32 goals in 20 matches across all competitions since Ruben Amorim’s first game in charge, an average of 1.6 goals conceded per match.

Only Tottenham (36), Southampton (35), and Leicester (34) have conceded more goals among Premier League sides than the Red Devils during this time.

"United got out of jail," Keane said on ITV. "Don't be fooled by it.

"You have to praise them - Manchester United are in the next round of the cup - but if they keep performing like that...the performance itself was nowhere near good enough.

"The subs made a difference. They played a lot more direct and more forward passes, but they should do more. They rode their luck."

Amorim said after the game that he was happy with the result but not with the performance, with Premier League strugglers Leicester playing well at Old Trafford. 

Though the Foxes only managed an expected goals (xG) total of 0.9 from their six shots, they were able to cut through United with ease at times, something Keane went on to highlight in his analysis. 

"The manager is obviously really frustrated with the performance. He mentioned about having no energy, that's the bit I don't understand," Keane added. 

"Whatever about the tactics and players trying to settle in and lack of confidence, but you've got to play with energy.

"Your starting point has to be energy and enthusiasm, and then you take it from there. If you've got no energy, it doesn't matter what system you're playing, you won't get near anybody.

"It's all well and good playing in possession, but you have to close people down. Leicester were getting plenty of joy.

"We've seen two bad teams there tonight. Any team with a bit more quality than Leicester would have got the job done. United rode their luck."