Nottingham Forest defender Jack Hobbs says the first-half display in the 3-2 defeat at Fulham was not good enough.
Forest trailed 3-0 after 35 minutes but a Henri Lansbury goal late in the first period sparked a spirited comeback that could easily have earned a draw.
Hobbs told BBC Radio Nottingham: "We put up a good fight in the second half but the first half was not acceptable.
"Collectively, we were all off it. We need to be a lot better. We were slow, lethargic and just not sharp enough."
Ross McCormack's first-half hat-trick put Fulham in complete control at Craven Cottage.
But Lansbury's second goal - a fine strike from Michail Antonio's pass on 62 minutes - made it 3-2.
And Stuart Pearce's side had several chances to equalise, notably when Britt Assombalonga missed a simple close-range header.
Hobbs said the improvement could not disguise how bad Forest were in the opening half.
"We never got to grips with it," Hobbs said. "We were all in between doing jobs and we gave McCormack too much space and he punished us clinically.
"We need to make more tackles, be more disciplined, we need to communicate and we need to get in faces. When we did get the ball back, we gave it away far too easily.
"We are massively disappointed with how we played in the first half."
Hobbs continued: "We came out in the second half and did what we didn't do in the first half. We created some good chances. You try to look at the positives in the second half and we could have snatched a point, but it's difficult to look beyond that first half.
"After the euphoria of Saturday [a 2-1 victory at local rivals Derby County] I don't know why we started so slowly. We were keen to build on that. In the second half we were all over them but we have to find out why we started so poorly."