The homegrown talent is heading to Napoli, where he will play for coach Antonio Conte.
Even though Ten Hag has often relied on McTominay in his two seasons in charge, he decided to cash in on the midfielder to make room for new signings.
Ten Hag stated on McTominay getting a warm reception in Naples: "It's a little bit mixed. I'm very happy for him and it's also for us, but it's mixed, because I wouldn't prefer to lose him, because he is Man United in every vein.
“He was so important for our team, for Manchester United. He was here for over 22 years. Unfortunately, it's the rules.
“We have to discuss the rules when you have to do sells and then, obviously, homegrown players, Academy players, they bring more value. That's not the right thing to do, but yeah, I think for everyone, for all parts, it's a good deal.
“For Scott, he's happy with it. Of course, for Napoli, a very good player. But also for us."