Few people understand McInnes as thoroughly as Docherty, who partnered him at St Johnstone and Aberdeen across more than a decade.

The ex-Dundee manager feels McInnes' strong competitive drive would enable Rangers to challenge Celtic closely until the season concludes.

At the split last season Rangers sat second, a single point behind Hearts and ahead of Celtic. Rohl described the remaining fixtures as five cup finals, yet his team lost four and finished well back in third.

Concerns over Rangers' mindset have persisted for years, and Docherty believes McInnes' determination could address them.

"Derek is a hugely competitive person," he added. "You saw that last year, when people thought his team were going to disappear.

"Purely through him and the recruitment he did they were competitive right the way through.

"I've got no doubt having that edge and having played at Rangers and having that affinity with the club, it will be a fantastic appointment.

"It is that mentality, you saw it in abundance last year. You've seen it all through his career, the amount of second-place finishes to Brendan Rodgers' Celtic with an Aberdeen team.

"And last year, every time Hearts were written off they would come up trumps."

Former Rangers and Dundee striker Rory Loy views Rohl's departure and McInnes' arrival as the ideal outcome for Ibrox.

"To think three or four weeks ago, some Rangers fans - given the decline after the split - were looking to move him [Rohl] on," he told the Scottish Football Podcast.

"To get money for him and to use that money to recruit Derek McInnes, I don't think it could have fallen more favourably for Rangers.

"The one thing Derek McInnes will bring above all else is the one thing that's been levelled at Rangers for the last decade - that's what is between the ears, that's mentality."

With Martin O'Neill now Celtic manager after securing a league and Scottish Cup double last season, Rangers face another test against their rivals' dominance.

As a manager McInnes has secured only the League Cup with Aberdeen in 2014 and the Championship title with Kilmarnock.

Yet his spells at Aberdeen, Kilmarnock and Hearts show a pattern of maximising squad potential against better-funded sides.

At Pittodrie he lost cup finals and the league to Rodgers' strong Celtic side, while Kilmarnock claimed Old Firm victories en route to Europe in McInnes' second year.

He then guided Hearts to their highest points total before they fell short late on against O'Neill's Celtic last season.

"His one issue may be is he's coming up against a powerhouse when it comes to these things in Martin O'Neill," Loy said. "He has a proven track record. To win seven on the bounce last year to win the title was unbelievable.

"I genuinely believe that if Derek McInnes was the Rangers manager going into the split, they don't collapse. They might not have won it - but I don't think they collapse. They take it to the last day at the very least.

"And with Martin O'Neill in charge, he has a proven track record, I think it has all the ingredients for nip-and-tuck, last game of the season stuff."

Docherty concurs that McInnes at Rangers would make next season compelling.

"If it does happen and Martin O'Neill is in place at Celtic and Derek McInnes is in place at Rangers it's going to be one hell of a title race this year," he added.

"Derek's strength is his longevity. He's been a manager for 18 years. For 15 years I was assistant to him. It's incredible to have that longevity and that amount of success."