Ex-Rangers midfielder Derek Ferguson thinks Ally McCoist's mental strength has helped him overcome early setbacks to win his first Old Firm test.
McCoist's side recovered from a 2-1 half-time deficit to defeat Celtic 4-2 and go four points clear at the top.
"He has had a lot of stick early on in his managerial career, but one thing about Ally McCoist, he has great mental strength," Ferguson told BBC Scotland.
"Great believe in his own ability - not just as a player but a manager too."
McCoist the player - and as assistant to Walter Smith until this season - developed a cheeky chappie image that Ferguson says hid a deep desire for success.
"He was one of the most fired up players before not just Old Firm games," said the former Rangers, Sunderland and Hearts midfielder.
"He's probably not the best player I ever played with, but what he had and what I think he will take into management, was mental strength - I have never seen a guy or a player like that.
"I go back to the time when I think we were playing at Ibrox against Dundee and John Brown scored the winner for Dundee and the whole stadium had a go at Ally.
"I remember sitting in the dressing-room beside him and the guy was on his knees.
"He was in tears and I thought to myself that night, he will never come back from this, but look what he went on to do - he became a Rangers legend."
While Rangers have started the defence of their domestic title in winning form, McCoist has come in for criticism after failures to qualify for either the Champions League or Europa League group stages.
"That result will do him the world of good and I can only imagine, he is such a likeable guy, all the players in that dressing-room will be absolutely delighted for him," said Ferguson.
"Ally McCoist has went in there at half-time and, whatever he said to the guys, they have taken it on board and you have to say they were absolutely on fire."
While Ferguson recalled how Terry Butcher, Chris Wood, Ray Wilkins and Graeme Souness would literally would take underperforming team-mates "by the scruff of the neck", striker Steven Naismith said that the McCoist-era dressing-room was less physical.
"Even over the last few years under Walter Smith, there was not much shouting and balling either," said the Scotland striker who scored twice on Sunday.
"We have a good group of boys who know what it takes and we are the first critics of ourselves."
Naismith admitted that criticism of McCoist had helped inspire the team before the game - and that they wanted to pull together to help goalkeeper Allan McGregor overcome the mistake that allowed Badr El Kaddouri to put Celtic 2-1 ahead.
"That gave us a wee extra bit at the start of the game," he said.
"You see the pressure he is under at the start, but I think that comes with the territory of being an Old Firm manager.
"He has just got on with it. Nothing has changed about him and on Sunday it was just a case of going out and doing it for him and, at half time, it was more about doing it for the goallie as well."