"After 20 years of football, I'm still the kid I was". We're the ones who go on the pitch.
"If you want the truth, I think it was honestly horrendous", Shaw said.
Mourinho was also quizzed about a report which claimed he was already preparing for his Old Trafford exit after receiving a call from Zidane, the favourite to replace him.
But the move now appears an expensive mistake with Mourinho plotting to offload the Chile worldwide.
Mourinho redirected the question from a Spanish reporter to the journalist that wrote the story, joking at a packed press conference that he had "put a bug on my telephone".
Zidane has since been on a sabbatical, but recently stated that he will soon coach again.
Manchester United have lost only once in eight previous meetings with Valencia in all competitions (W2, D5), and never in the Champions League (P6, W2, D4, L0), with this their first encounter in this competition since December 2010, a 1-1 draw at Old Trafford.
He was then reportedly admonished by Mourinho in front of his team-mates for his poor form and was the only outfield player who travelled to London for the West Ham debacle left out of the matchday squad.
"The performance on the pitch in my opinion is the outcome of many factors", added Mourinho.
"I think individually and as a team we were terrible".
"I like that perspective, but I don't agree totally".
"We didn't play well on Saturday, but we gave our best in that moment", Matic said.
As for Mourinho, Arnautović added: "I have nothing to say". "We're the ones who go on the pitch".
"For me, I played one of the worst games since I signed for Man United".
And Matic admitted he too fell well below his normal standards at the weekend.
"This game was really bad but everyone has a responsibility for that".
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