Erik Ten Hag says Manchester United did not show "fighting spirit from minute one" in last weekend's defeat at Brentford - as the focus turns to the Monday Night Football clash with Liverpool, live on Sky Sports.
United were well beaten 4-0 by the Bees to leave them bottom of the Premier League table.
Ten Hag continued his criticism of his players and that performance at his press conference on Friday.
"I was definitely not happy," he said.
"The basic stuff has to be good and that has to start with the right attitude.
"You need fighting spirit on the pitch and I didn't see it from minute one.
"The players didn't play good, a lot went wrong. You don't have to talk about anything [tactical] when the attitude is not right."
Ten Hag added he is aware of United's intense rivalry with Liverpool and instructed his side to "act as a team" to gain confidence after a poor start to the season.
"I know the rivalry," he said. "We are the rivals. We have to win every game but especially this game. It starts with yourself.
"Act as a team, follow the results and principles and from that you get confidence."
