The Royals boss has coined the clash as one of the few incredible games they have had this season after seven goals were scored in the opening 34 minutes at the Madejski Stadium
The Royals took the lead twice in the game, but a quick fightback from the visitors silenced the Madejski Stadium faithful with the Red Devils running out 4-3 winners, with all seven goals coming in the first 34 minutes.
Despite suffering a defeat, McDermott is confident his side's performance against the Premier League leaders is a sign that they have enough quality to hit in form in the coming weeks.
"It was an incredible game really, and we've had a few of those this season," he told Sky Sports. “We played for our supporters, they want to see us get the results and they will come.
"I was proud of the efforts and that first-half performance from our players. It wasn't just effort alone, there was quality as well in the way we passed the ball.
"I'm disappointed that we haven't come away with anything, but that's the nature of this league. Last season we were winning game after game, this season we've just got to hang in there. We have to be different here and get the results whatever way we can."
A win over Sir Alex's side would have lifted Reading out of the relegation zone, but the defeat sees the Royals sit just one place above rock-bottom QPR with nine points.
McDermott added: "The lads will be disappointed today but we know the calibre of the opposition in this division, we know the calibre of Manchester United. Manchester United are synonymous with everything that is good about football.
"They have top quality players, [Wayne] Rooney, [Robin] van Persie, [Ashley] Young, the list goes on. We are Reading, we have to do things differently and do things our way.
"You see the confidence levels from our players, and look at the way we passed the ball and got crosses into the box. We caused them a lot of problems today and I thought with the late set play [Sean] Morrison was going to score."