Ralf Rangnick branded Manchester United's 4-0 thrashing by Brighton as 'humiliating' and 'unacceptable'.
United conceded four goals for the sixth time in their last 30 Premier League games to finally end their last chance of qualifying for the Champions League next season.
The battering by Brighton possibly marked the nadir of an apocalyptic season and the United supporters chanted "You're not fit to wear the shirt" in the second-half.
READ MORE: Bruno Fernandes responds to Manchester United fan chant in Brighton humiliation
Rangnick likened the defeat to United's 4-1 loss at Watford in Ole Gunnar Solskjaer's final match in charge on November 20.
"To start with, it's important we apologise to our supporters who came all the way from Manchester here to Brighton," Rangnick said. "We were just not good enough from start to finish. The performance was not only poor, it was extremely poor.
"We knew that even from our first game that we played at home in the first half that Brighton is a very flexible, tactical team, always trying to play through your lines and to be creative.
"So we knew it was not enough to just enjoy yourself in possession of the ball, the problem was we were not that often in possession of the ball, in order to be in possession we should have won the ball but we gave them far too much space and time.
"And at half-time, if we're honest the only good thing was the result for us, it was 1-0. At half-time, the question for me was what are we going to do and bring on two new players, that was clear. But do we change the formation into a 3-5-2 or do we take the risk to play in a 4-4-2, which we did in the end.
"In hindsight, maybe that was a little bit too much of a risk. I take responsibility for that, if that was the case. I think in general it was just the problem we had in earlier games, for example at Everton and at Liverpool, but this was a different level again.
"We were not good enough in defending as a team and taking the ball away from the other team, this was our biggest problem today and why we didn't create many chances. The only time we had chances ourselves was in the last 20 minutes when we were playing in a 3-5-2."
When asked if the players were uncaring, Rangnick replied: "No. No. I have to defend the players here, I don't think they are. I saw them in training, I saw them against Brentford, again after beating Brentford at home, also a team who are not that bad in possession of the ball and had quite a few good results.
"For me, it was clear not to change anything, or change that winning team. We had a good week in training, with a good atmosphere and focus on the training sessions but, as I said, I remember watching the game against Watford away, 4-1, who are now relegated, and this looked very similar to what happened today.
"For me, the problem is how to defend as a team and in this league, if you play against good teams and Brighton is a good team, if you do not defend properly, if you just let them play and give them all the space and time in the world, this is the result.
"It was a humiliating defeat today and even more so for a team like Manchester United, that was the second-highest defeat in my whole career as a coach in the last 35 years.
"But it's not only that you lose 4-0, it was the way that we played and this is just unacceptable, very difficult to deal with and cope.
"Full responsibility on my side for the performance but it's difficult, really difficult why we played like we played against Brentford on Monday and played like we did today."
United are certain to end the season with their lowest points tally in the Premier League era and they have conceded the most goals in a top-flight campaign since 1978-79. When it was suggested to Rangnick this season had been 'disastrous', he agreed.
