The 18-year-old won man-of-the-match on his first England start in Tuesday’s 2-2 draw against Belgium to put himself firmly in contention to be selected in Gareth Southgate’s squad for Euro 2024.
Mainoo has also been a rare shining light this season for United, becoming a key member of Ten Hag’s midfield since making his first Premier League start in November.
“I thought it was very good, but we are not surprised,” Ten Hag said Friday of Mainoo’s international bow. “We have seen what he is capable of, that he can very quickly adapt to high levels. It looks very natural.
“We are very happy for him and of course a little bit proud. I would say very proud.
“It’s great for the academy of Manchester United that they bring up a player so young going into the national team. That is a big compliment for the whole club.”
A thrilling 4-3 win over Liverpool in the FA Cup quarter-finals prior to the international break has helped keep United’s season alive.
The Red Devils are now big favourites to reach the final for a second consecutive year after being drawn against second-tier Coventry in the last four.
United are also hunting down Aston Villa and Tottenham in the hope of qualifying for the Champions League next season.
Ten Hag’s men are nine points adrift of fourth-placed Villa with a game in hand and six behind Tottenham.
A top four finish would guarantee a place in the Champions League, but fifth may also be good enough if English sides finish the season strongly in the European competitions.
Injuries have played a big part in a difficult second season for Ten Hag and United could be boosted by the return of centre-back Lisandro Martinez for Saturday’s visit to Brentford.
The Argentine World Cup winner has made just 10 appearances all season due to serious foot and knee injuries.
“We missed him every game because he brings a composure in the team, a calmness in the team,” added Ten Hag.
“And at the same time, (he brings) a winning attitude and he can express this very clearly. He can transfer this into the team and that contributes a lot to our levels.”
