The Red Devils recorded one of their heaviest defeats in recent memory as Darwin Nunez, Cody Gakpo and Mohamed Salah all helped themselves to braces and Roberto Firmino added the icing on the cake on a chastening afternoon at Anfield.
The defeat came just a week after Erik Ten Hag's side had ended a six-year wait for a trophy by beating Newcastle United 2-0 in the Carabao Cup final at Wembley.
The manner of the defeat was difficult to comprehend, given the tie was level just two minutes before half time but by the 50th minute, United were three goals down.
Speaking to MUTV, Shaw said: "Out there on the pitch, I felt embarrassed for us players, for the fans who were supporting us and who were watching at home. 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 [Carabao Cup] and, in the last couple of games, we haven’t been our normal selves – 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. We showed no personality and no mentality. For a big team to come here, we need to do better."
Manchester United will return to action on Thursday against Real Betis in the Europa League.
