Nottingham Forest's first-half display against Charlton made manager Stuart Pearce "sick to the stomach", according to winger Michail Antonio.
Pearce's side have conceded first in eight of their last 10 matches and slipped to 10th in the Championship table after Saturday's 1-1 draw.
"Even at the end of the game, he still talked about the first half," Antonio told BBC Radio Nottingham.
"He told us it's not good enough. He said it made him sick to the stomach."
Forest won five of their first seven Championship fixtures, but have won just two from 13 in the league since beating Fulham 5-3 in mid-September.
And Pearce warned his players their inconsistency is threatening their hopes of promotion.
Antonio, who has scored 10 goals in 22 games since joining from Sheffield Wednesday in the summer, added: "In every game this season, we've finished better than the team we've played. We can't rely on that.
"If we keep turning up one day and not another, then we're not going to get what we want and that's promotion."