Former Cowdenbeath and St Mirren defender McGregor put pen to paper on a one-year deal with the SPFL League One champions this week.
The 28-year-old was overjoyed after landing a dream move to one of the biggest clubs in Britain and is looking forward to the new season.
However, many Light Blues fans were not quite so enthusiastic about the capture of the centre-half on a Bosman transfer for McGregor has suffered cruciate ligament injuries in both of his knees during his often difficult four-year stint with the Buddies.
And there have been doubts expressed that he is fit enough or good enough to play a significant role for Ally McCoist's team in the Championship.
Yet, the coach who helped to resurrect the player's career has seen him defy the odds and prove his doubters wrong on numerous occasions over the years.
Former Hearts player Brian McNaughton worked at Cowdenbeath when McGregor was just starting out in the game there.
And when the youngster found himself on the bench at Central Park he immediately snapped him up for the Junior side he had taken charge of.
The Edinburgh-born lad did not look back after dropping down to that level and now, just six years on, he has been snapped up by the Glasgow giants.
McNaughton has no doubts whatsoever that Gers fans will grow to love the committed and skilful stopper in the coming months.
He said: "If fans see somebody who gives everything in every game, like Darren does, then they will respect him. Fans like to see players who put in a lot of effort.
"Plus, remember that Darren has been playing in the Premiership. I am sure he will take playing for Rangers in the Championship in his stride."
McNaughton has enjoyed seeing how McGregor has progressed since he worked with him in the East Region Premier League with tiny Arniston Rangers.
The player took on Junior minnows from Dundee, Edinburgh and Fife for over a year and grew in self-belief and developed as a player as a consequence.
McNaughton said: "I had been one of the coaches at Cowdenbeath and when I heard Darren had dropped out of the first team I called him and said he needed to get games.
"He was certainly good enough to play senior football in my mind. But you tend to find that a lot of managers will go for experience over youth when it comes to centre-backs.
"I told him Darren to come and play with Arniston and that is what he did. I had to convince him to drop down a level and play instead of sitting on the bench.
"But he took my advice and his confidence grew as he got games. When Mixu Paatelainen left Cowdenbeath, Danny Lennon replaced him and took Darren there.
"He was such a good player for Cowdenbeath and he has maintained his progress with St Mirren in the top division. Now he has joined Rangers. It is quite amazing really."
McNaughton, who himself moved from a Junior club to a senior side when Hearts snapped him up from Broxburn in the 1980s, has seen McGregor mature as a player over the years.
And he feels with the player's total dedication to his profession and desire to improve he will cope with the step up to Rangers in the 2014/15 campaign. He said: "Darren has always been a prospect. He always had great potential. He was one of the quickest players in the Cowdnebeath side when I first saw him.
"But he was quite raw back then. He has worked hard on all aspects of his game. He has worked hard on his physicality especially.
"He could be quite rash. If he saw the ball he thought he had a divine right to win it. He was very aggressive. Not in a malicious way, mind. He was always fair.
"But if he saw the ball he would put his full force into a challenge and sometimes he would come off the deck to win the ball which you just cannot do. He could be rash.
"When I worked with him he was still very youthful. I am sure he would be the first to admit that he didn't always make the best decisions on the park at that stage.
"I know how hard Darren worked to get to Rangers. He will tell you himself that he is not the most naturally gifted player. The most pleasing thing about it all is that he is a brilliant lad."
McNaughton, who is currently working with Dalkeith Thistle, believes the success of McGregor shows that senior clubs should keep an eye on the Junior ranks.
He said: "There is a lot of talent in the Juniors. There are boys there who are only not playing in the senior game because of their employment. There are gems like Darren to be unearthed.
"The Championship will be a great league this season with Hearts and Hibs in there with Rangers, but Darren has excelled in the top division in Scotland and I am sure he will do well."