Manchester United's level of performance has dropped since the team lifted the Carabao Cup, defender Luke Shaw said after they were thrashed 7-0 by rivals Liverpool in the Premier League on Sunday in their heaviest defeat in 92 years.
United travelled to Anfield on an 11-match unbeaten streak but suffered the club's worst loss since losing 7-0 to Wolverhampton Wanderers in 1931.
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The defeat came a week after United claimed their first trophy since 2017 by winning the Carabao Cup, having beaten Newcastle United in the final.
"Out there on the pitch, I felt embarrassed for us players, for the fans who were supporting us and who were watching at home," he told MUTV.
"To watch that second half ... I can only apologise for that, us, as players, have to own it, we have to stand up and accept that it was nowhere near good enough.
"It was completely unacceptable. Our standards have clearly dropped since we won that trophy, and in the last couple of games we haven't been our normal selves."
United conceded six of the seven goals in the second half as Cody Gakpo, Darwin Nunez and Mohamed Salah all scored twice for Liverpool.
"We need to find the good things we were doing before and bring them back because this hurts a lot, and it's really unacceptable what we did in that second half," Shaw said. "We showed no personality and no mentality."
The result boosted Jurgen Klopp's side's hopes of a top-four finish as they rose to fifth in the Premier League table, three points below fourth-placed Tottenham Hotspur.
Marcus Rashford also tweeted about the result on Monday and said: "I wish we could play a game today to try and put things right. The result is the result, and we can't see past that!
"We must not let it define our season. We have to trust the process and stick together."