Ralf Rangnick labelled Manchester United's defeat by Liverpool "embarrassing, disappointing and humiliating" after they were hammered 4-0 at Anfield on Tuesday.
Mohamed Salah netted a brace with Luis Diaz and Sadio Mane chiming in with goals to complete the route. Gary Neville and Roy Keane laid into Man United after the match, with the former calling the Red Devils a "waste of space" and the latter admitting he is more "sad" than angry these days.
Speaking after the game, Rangnick said: "It's embarrassing, it's completely disappointing and also humiliating, but we've got to accept that they're six years ahead of us. The team needs to be rebuilt - it's clear. I think a game like the one today showed that in a very drastic way that this rebuild is necessary."
He added: "The first half we were just not up to it. The first goal wasn't part of the game plan to be that high up, conceding a transitional moment after 4 minutes. We had all the players at the halfway line.
"Our left side was completely open. In the first half, we were nowhere. If you don't try to win second balls, you will be second best in all possible areas."
"For the third goal, we played a ball right into their pressing zone. They are one of the best teams in the world right now, we’re far away from that. We're not physical enough. I'm pretty sure our players knew the importance of that game to our supporters, but in the first half, we weren't on them at all.
"Liverpool have made a lot of good decisions, we're not in that area right now but we have another five games to go. Liverpool only needed two or three transfer windows and if you know what you’re looking for it doesn't have to take four or five years. Here in our club, it has to start this summer."
Paul Pogba limped off in the ninth minute for United with a leg injury. Providing an update on the Frenchman, Rangnick said: "He pulled his [calf] muscle. This is now the seventh or eighth player missing out with injury although we only play in one competition - this has to raise some questions. I’m not happy about that at all."
On Liverpool's dominance over the Red Devils, he added: " Liverpool are playing in four competitions and have nobody injured. This has got to do with how you train, what you do, and what measures you take in order to recover to be fully fit. Those are questions that need to be asked and answered."
Liverpool and Manchester United fans paid tribute to Cristiano Ronaldo on the seventh minute after the Portugal international announced his baby son had passed away on Monday.
Rangnick said of Liverpool joining United in the gesture: "The atmosphere is great, they love their team and [the fact] they joined in after seven minutes shows they respect that football is more than just supporting one team."
