Celtic manager Neil Lennon threatened to single out some of his players after a 0-0 draw with Hibernian left them 12 points behind leaders Rangers.
"A few have been consistent like Ki [Sung-Yueng] and Joe Ledley. But there are others who are happy to go along, riding on their backs," Lennon said.
"I have to speak to them and out them, basically.
"I am really angry. They let the game drift away from them and that is not acceptable."
The performance came just three days after Celtic hammered Hibs 4-1 in the Scottish Communities League Cup at Easter Road.
The draw compounded a poor day for the Hoops after Glasgow rivals Rangers stretched their lead at the top of the league with a 2-1 win over Aberdeen.
Lennon added: "I am not happy with some of them at the minute. I don't think they are giving enough in terms of the quality of their play or effort and I will speak to them individually and tell them what I think and I am looking for a response from them.
"But you ask them questions at times and you don't get answers."
Defender Mark Wilson defended his manager. "It is harsh words but that's what he thinks," he said.
"I don't like slagging my team-mates off but we have to do better.
"Football is a result-driven game but we don't want that [Lennon sacked]. We are firmly behind the manager and we love working with him and the coaching staff."
Despite Celtic's struggles, the Northern Irishman has refused to contemplate walking away from his position - even with rumours linking him to the vacant Leicester City manager's post.
"The only way I would leave the job this season is if I decide I am not taking the club forward or I am not getting the performances that the fans merit.
"Today, I am not hugely concerned about my position, it's more of a question of why I can't get these players to be as consistent as last season."
Lennon admitted that the form of Gary Hooper was a concern, the striker having failed to match last season's level following a spell out through injury.
"I don't know if it is a fitness thing," he said. "He keeps telling us he is all right, but at the minute he is not as bright or sharp as he should be.
"I don't know if it is an after-the-fact from the injury, but he looks short of what he should be.
"We were poor going forward. The ironic thing is we keep a clean sheet and we can't win the game.
"Our play in the final third was nowhere near good enough."