Mainoo has started 15 of United’s last 16 games, including the previous 12 in the Premier League, and undoubtedly features in Ten Hag’s first-choice midfield.
His stock soared higher after the dramatic FA Cup quarter-final win against Liverpool earlier this month when Gareth Southgate suddenly called him up for the England senior squad.
Mainoo made his debut in the final 15 minutes of the Three Lions’ 1-0 defeat against Brazil before earning his maiden start in the 2-2 draw with Belgium at Wembley Stadium, winning the Player of the Match award.
He has emerged as one of Europe’s most talked-about teenage talents, and his return from injury in November has helped improve results at Old Trafford after a disastrous first half of the campaign in his absence.
But Ten Hag might have to travel to the Gtech Community Stadium without Mainoo on Saturday if he hasn’t recovered from an illness picked up earlier in the week.
The Dutchman confirmed that Mainoo sat out United’s training session on Thursday and that he hadn’t fully recovered when he reported to the club’s Carrington base on Friday.
“I don’t know, we hope [he will be fit]. Today, he is here, not fully recovered, but we still have many hours before tomorrow, with kick-off at 8pm,” Ten Hag explained at his press conference.
Casemiro could return to action after missing the 4-3 triumph over Liverpool at Old Trafford with an injury. He didn’t feature in Brazil’s fixtures, but murmurs suggest he’s now available.
If that’s the case and he starts alongside Mainoo and captain Bruno Fernandes, Ten Hag will have quality on the bench in Scott McTominay, Mason Mount and Christian Eriksen.
The United boss has also hinted that Lisandro Martinez could re-enter the fold after his latest injury setback, which has seen him sidelined for the past two months.
He said: “Yes, there is a chance [he could be available]. We have missed him every game because he brings composure to the team and a calmness to the team.
“At the same time, a winning attitude and he can express this very clearly. He can transfer that into the team and that contributes a lot to our levels.”
United start the weekend six points behind fifth-place Tottenham Hotspur and trail Aston Villa in fourth by nine, having played a game less than Unai Emery’s side.