Daniel Candeias admits Rangers’ players have to take a long look at themselves after flopping against St Johnstone yesterday.
The Ibrox men now face Kilmarnock in a Scottish Cup fifth-round replay on Wednesday.
Candeias issued an apology to supporters and demanded a big improvement from his team-mates.
He said: “The whole team is disappointed with the result and performance against St Johnstone.
“We now have to look at ourselves for the mistakes we made in the game.
“We need a reaction on Wednesday night. We have to put in a great performance and win the game.
“There are too many games left to talk about the title but, of course, if you play like we did you don’t deserve to win the league.”
Candeias is a close friend of Alfredo Morelos but refused to use his absence as an excuse for the no-score draw.
He went on: “Alfredo is important for the team – he’s our top scorer – but we have great players in the team without him.
“When he’s not there we have Lafferty and Defoe.
“They’re great players but everyone was disappointing.
“I had a chance to score in the second half but when the team aren’t playing well, you have mistakes.
“I’m sorry for that performance.”
Meanwhile, Lassana Coulibaly looks unlikely to have a long-term future at Rangers.
Steven Gerrard maintains the way Neil McCann coached Glen Kamara at Dundee helped secure his move to Ibrox.
The Finland international, who made his debut yesterday, could make it difficult for Coulibaly to get game time, lessening his chance of a permanent move from Angers.
Gerrard said: “Glen’s been well coached at Arsenal but I also think I have to mention Neil McCann.
“He has done an excellent job in taking him from academy football to the next level and introducing him to the real world.”
The Rangers manager admitted money for a transfer fee could get in the way of signing Coulibaly.
He went on: “It’s a big consideration for us. We like the player but there’s a lot of things involved – price, salary, his contract situation at his club.”