Russell Martin spoke scathingly about "egos" and "self-preservation" among his players after Rangers dropped two points at Motherwell on the opening day of their Scottish Premiership campaign.
Gers skipper James Tavernier headed in from a corner in the 14th minute but the Ibrox side failed to kick on and eventually succumbed in the 87th minute when Emmanuel Longelo drove in a deserved equaliser for a 1-1 draw.
It is the third successive season that Rangers have failed to win their opening game, and on Sunday they could fall behind Old Firm rivals Celtic when the champions host St Mirren.
In a spectacular post-match summation of his players, Martin, whose side progressed to the Champions League third qualifying round against Viktoria Plzen with a 3-1 aggregate win over Panathinaikos on Wednesday, said: "I'm very disappointed and a bit hurt and a bit angry at a lot of stuff I saw.
"Motherwell were really good, credit to them. But I said to the players, the problems haven't been tactical, yet. They've been mentality, about energy, about courage, intensity, aggression, to play.
"We haven't started games well enough in the first half in the two European games and then showed a bit more willingness to trust the detail in each other and work.
"And then today, we go ahead and play some OK stuff. Every time we get in the final third, we turn the ball over and make crazy decisions.
"They're either selfish decisions or they're based on anxiety, so we need to get to the bottom of that.
"Because there was far too much stuff that we haven't worked on or haven't seen.
"It's not me digging them out. I take full responsibility for it. But that hurts me more than anything.
"The problem should be tactical, it shouldn't be mentality. So we have too many guys that slip into self-preservation mode. And I think it's been a fact of this club for the last few years for sure.
"So when it's going well, you're all-in, you want to run, you want the ball. It's nice, but when it's not going well, you don't want to run so much, you pick and choose when you want to run.
"You pick and choose when you want to compete and mark your player from a throw-in or a corner.
"You pick and choose when to run back, and it's unacceptable for this sort of club. And for us as a coaching staff, this is not acceptable.
"We're six weeks in, there will be issues. But the issue today is purely mentality.
"So too much ego, too much self-preservation, and you're either all-in all the time or you're not. And if you're not, you just won't play very much."
Motherwell's new boss Jens Berthel Askou, a former teammate of Martin at Norwich who was taking charge of his first league game, was disappointed his side did not take all three points.
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"I said to players, I was very disappointed on their behalf that they didn't get the win at the end because we did everything we could to get the win," he said.
"But again, that's down to quality also in these small situations and we'll keep working on that and sharpen that up.
"I think they gave themselves the opportunity to win, and that's where it starts with the effort and with the desperation to go forward and to punish them on their transitions and to really work extremely hard throughout the entire game.
"I was very happy with that and I know that if we are able to put our performances like this over time, that there will be many other opportunities to win games."