Watford manager Aidy Boothroyd is relaxed ahead of his side's FA Cup semi-final against United, despite watching the Reds tear Roma to shreds on Wednesday night.
The Hornets boss was among the crowd as United swept into the semi finals of the Champions League at the expense of the Italians.
However, he told Sky Sports News: "I'm actually quite relaxed about it. I was privileged to be in the crowd to watch the game. I thought they were absolutely outstanding.
"They're good, without a shadow of doubt. They were excellent. It's going to be a tough call."
Despite United's stunning return to form, Boothroyd is relying on the FA Cup's famous romance to act as a leveller at Villa Park.
"The FA Cup is all about shocks," he said. "Because of the way the game is with the money these days we tend not to get that many, but who knows maybe it's our year.
"We've got to make sure we're all ten out of ten on the day. To make sure the game is a good game and it's a game that either team can win."
On-loan United goalkeeper Ben Foster is prohibited from facing his parent side, but Boothroyd is confident that second-choice goalkeeper Richard Lee will deputise ably.
"He has done it before," said Boothroyd. "He came into the first team against Manchester United and did really well.
"Part of being a number two is that you have got to be very focused and work exceptionally hard to make sure you can go straight back into it.
"I know playing reserve-team football is nowhere near it but he trains with the first team every day because he is very much a part of our plans.
"It takes a certain type of mentality to be able to come in and perform like he does. It won't be a problem for him."