Mainoo started for the 10th consecutive time in Sunday’s 3-0 victory against the Hammers, which saw United leapfrog their opponents into sixth in the Premier League.
He has wowed football fans in recent weeks with his well-rounded ability, sitting at the foot of Ten Hag’s midfield in Casemiro’s absence before enjoying a box-to-box role since the Brazilian returned.
Mainoo’s composure on the ball, reading of the game off it, and passing range have caught the eye this season.
The Stockport-born star also has goals in his locker, as he demonstrated by scoring an incredible 97th-minute solo strike in last Thursday’s dramatic 4-3 win at Wolves.
United’s latest prodigy has been the centre of attention recently, with cameras aiming at him from all angles in the hope he will pull off another headline-worthy act.
But what he was spotted doing off camera during United’s triumph over West Ham makes for just as impressive reading.
The Red Devils sprung a surprise by drifting away from their usual erratic, direct style of play by lowering the tempo against David Moyes’ side.
Bruno Fernandes has made it his role to regularly attempt risky forward passes to try and unlock a chance for one of his speedy attacking team-mates.
But many of the United captain’s passes went sideways or backwards against West Ham. At one point, he looked frustrated at Casemiro for lumping the ball upfield, as if they had been instructed to take more time.
According to The Athletic, Mainoo did the same to his team-mates on more than one occasion, producing a “calm-down” gesture when he felt the game was becoming too quick.
It’s claimed the teenage sensation also joined his manager in urging United’s players to keep the ball on the ground and avoid playing head tennis with West Ham’s towering stars.
Ten Hag has often called for control when publicly analysing games. For one of only a handful of times this season, he got what he wanted in the West Ham win.
And Mainoo’s intelligence and maturity were a significant reason for that, again providing optimism that he is a player that United can build around for years to come.