Aberdeen skipper Graeme Shinnie admits the Dons failed to turn up on the big stage yet again as their dismal run against the Old Firm continued.
Derek McInnes’ Reds were looking to open up a six-point lead over Rangers when they met in Glasgow on Wednesday night.
But a 2-0 defeat sees them drop to third, with Graeme Murty’s Rangers now in front on goal difference.
The result means Aberdeen have now lost all three clashes against the Ibrox men this term and five out of seven since the Light Blues made their top-flight return.
There has also been nine straight defeats to Celtic since Brendan Rodgers took over at Parkhead and Shinnie admitted he is getting tired of having to explain his side’s troubles against the Glasgow giants.
“It’s very frustrating,” said the Pittodrie captain. “Too many times I’m sitting here saying that.
“It’s easy for me to sit here and talk but it wasn’t good enough - again.
“We need to be more demanding of ourselves. We need to be more clinical at both ends of the pitch.
“When the second goal went in last night, we had four or five good chances to put some pressure on and one of them just has to go in.
“The goals we lost were sloppy as well. We need to do a lot better. It is not good enough.
“There was not much in the game. The goals that we concede are so frustrating. They give the other team a lift. And then at the other end we need to do better with the chances we had.
“At places like Ibrox, if you get opportunities, you need to take them. We didn’t, and we got what we deserved.”
Murty’s Rangers now have their noses in front in the race for second having boosted their squad with a number of new faces during January.
But Shinnie insists the Reds will not give up on reclaiming the runners-up slot they have held for the past three seasons.
He said: “We always knew it would be a fight for second spot.
“We need to pick ourselves up and go again on Saturday. That is all we can really do now. It was a very disappointing night but football is a job where you need to get going again and there is no bigger game than Saturday at home to Kilmarnock.
“I won’t need to lift the heads of the boys because they will also all want to bounce back on Saturday.
“We need to be better.”
Meanwhile the Dons have confirmed goalkeeper Joe Lewis did not suffer a broken leg against Rangers.
The Pittodrie number one had to be rushed to hospital after clattering into team-mate Anthony O’Connor as he brought down Josh Windass for a late penalty.
After the match, McInnes admitted he feared Lewis has suffered a serious injury but the club released a statement in the early hours of Thursday morning confirming he did not suffer a leg break.