"We started well," explained Erik Ten Hag in his post-match interview with BT Sport. "Then an unnecessary mistake and had a really bad 10 minutes.
"We have to learn from it. You let the crowd get alive, you have to avoid that."
Discussing the 3-2 win over Omonia in the Europa League, the Manchester United boss added: "It has to only be a warm up, on Sunday we have to react."
Goals from Marcus Rashford and Anthony Martial helped the Red Devils beat Omonia, who looked like a real threat on several occasions.
United face Everton on Sunday as they look to bounce back from a 6-3 loss to Manchester City.
Source: BT Sport