The Scotland international headed the opening goal after five minutes from an Alex Telles corner.
United, who made numerous chances to their starting XI, maintained the pressure for a period, but then saw their dominance slip and they struggled somewhat after the break.
“We started really well,” McTominay told BT Sport. “For the first half hour we were really good, we moved the ball. We just didn’t find it after that. Then in the second half, we didn’t play anywhere near our best. Tired legs, tired mind.”
On his goal, he commented: “We work a lot on set pieces, so see one of them going in is nice. I need to start scoring more headers, I’m six foot three!”
It was a night that McTominay is set to remember for the rest of his life, despite the overall performance, as he was named as captain from the outset of the game.
“When the manager told me, it was a surreal moment,” he said. “I’ve been at this club since I was five years old – so 18 or 19 years – so it’s a huge honour. I absolutely love the club, it’s been my whole life.
“The manager has been nothing but amazing since he came to the club. I’ve a lot to thank him for but the best way of doing that is putting in performances on the pitch. As long as I’ve got the manager’s trust, I’m happy doing my job.”
United face a critical week in their season, with a match against Burnley on Tuesday that will see them go to the top of the Premier League if they avoid defeat.
They will then tackle Liverpool in a top-of-the-table encounter at Old Trafford next Sunday.