Rangers were "done by a refereeing decision" as they lost 1-0 to Celtic in the first Old Firm game of the season, said boss Steven Gerrard.
Olivier Ntcham's second-half goal condemned Gerrard to the first defeat of his 13-game tenure.
But the Ibrox boss claims that fourth official John Beaton told referee Willie Collum that Ryan Jack was fouled by Tom Rogic in the build-up.
"He's shouting 'foul, foul, foul' down the mic," Gerrard told Rangers TV.
"I just assumed it would be given. For me it was a blatant foul and if we get that we maybe come away with a point."
Gerrard said he spoke to Collum after the match and that he thinks the referee will "change his mind" when he sees the incident again.
However, the Rangers boss did concede that goalkeeper Allan McGregor was fortunate not to be punished for flicking a leg at Celtic defender Kristoffer Ajer.
The pair collided amid a goalmouth scramble and Gerrard said he thinks the Scotland international "lashed out" and that he would "speak to him" about it.
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- 'Win will have bigger impact on Celtic than on Rangers'
'Next time, we will play for 90 minutes'
The defeat means Rangers are without a league win against their city rivals since 2012, while Brendan Rodgers remains undefeated in Old Firm derbies as Celtic boss.
The Ibrox side sit seventh in the Premiership - four points behind Celtic, and seven adrift of leaders Hearts - and have won just one of their opening four Premiership games.
Celtic hit the frame of the goal on four occasions, leading Rodgers to describe his side as dominant despite the tight scoreline.
However, given Rangers were thumped 4-0 and 5-0 in the previous two derbies, Gerrard was encouraged by his side's display at Celtic Park.
"I felt we were hanging on a bit [in the first half] but I thought second half we matched them, if not edged it," he said.
"We've been together for 12 or 13 weeks, but we'll improve and hopefully the next time Celtic come around, we can play for 90 minutes rather than just 45."
'Can't blame the referee'- analysis
Former Scotland defender Willie Miller on Sportsound
I thought there was contact [by Tom Rogic on Ryan Jack], but I wouldn't say it was a clear foul. I've seen fouls given, I've seen them not given, for that.
If you take the two incidents together, McGregor not being sent off and a possible free-kick in the build up to the Celtic goal, you can't blame the referee for the loss.
Allan McGregor, lashing out like that, should have been sent off, irrespective of whether Ajer has been a little bit naughty in the build up. The goalkeeper's lashed out and the match officials have got to see it, but they've not made the correct decision.
There's no doubt that could have changed the game because McGregor was outstanding.