A man lined up before a firing squad rarely has the luxury of deciding when the trigger is pulled.

Ally McCoist's decision to tender his resignation as the manager of Rangers and begin his 12-month notice period wrong-footed the forces massing against him. It was a left-field move entirely in keeping with events at a club where normality is abnormal.

In the hours that followed there were rumours and counter-rumours, information and leaks, but cutting through the fog of uncertainty was the simple, unalterable fact that McCoist had instigated divorce proceedings against Rangers. That alone made it a day when the tectonic plates moved in Scottish football's little world.

A cacophony had grown around McCoist in recent weeks. Attitudes hardened around him and although he brushed off vocal criticism and abuse - joking that he received worse in his early days as a player - the truth is that the recent scrutiny, hostility and ridicule washing over him was far darker, more personal and more sustained than anything he had endured as a young striker making his name in the early 1980s.

Only days ago he talked of being protective of his family when the abuse becomes personal. That, the team's struggles and the erosion of the club's infrastructure - the redundancies of colleagues and staff he liked - all ate away at him and were factors that took him to the brink. That famous quote about "we don't do walking away" was no longer relevant, and no longer an impediment to him taking the initiative.

McCoist likes to be liked and his popularity will be fully restored once he has some distance from the manager's office but, as Rangers have stumbled and staggered in his three-and-a-half seasons in charge, it was obvious that supporters' huge affection and respect for him was being corroded and polluted by his traumas in charge of the team. There are Rangers fans who will be relieved when McCoist is out of the dugout so that they can go back to thinking about him with their previous, uncomplicated adulation. When a team suffers the number of numbing humiliations against little teams that Rangers have, one man has to take the blame.

When a manager's results and performances are so exasperating that his own fans chant for him to "get tae f***" he doesn't usually get the privilege of saying yeah, okay, I'll go, but on my own terms. McCoist had the power to shape his departure because Rangers have been too poor to sack him because of the compensation fee that would involve.

The news that Rangers had turned down McCoist's resignation - supposedly because they could not afford to pay up even his notice period - was a typically daft new route for the story to take. Nothing is ever straightforward at Ibrox and one theory has it that those on the board who want rid of McCoist intend to embarrass him into waiving a full pay-off.

These situations are fluid and negotiations will doubtless take place swiftly to reach a compromise figure which would mean that he leaves within days. The timing of McCoist's departure will be agreed in due course. The real significance lies in his having reached the decision that his time is up.

Whether Rangers limp on with their broken ownership model, or Mike Ashley invests serious money, or others buy in to repair them, it won't be McCoist as the figurehead. He has been the last prominent, trusted link with Rangers' past and for that, if not for his football, some will mourn his departure.

McCoist will be remembered like John Greig, as an iconic Rangers player and figure whose spell as manager was flawed and undistinguished. Yes, back-to-back promotions were secured but that was a bare minimum given the amount of investment McCoist was allowed to make on players' salaries.

The mismatch of finances with all other teams in the lower divisions was astonishing and McCoist was often criticised for not making the sacrifices - the squad stayed in top hotels before games - Rangers clearly required.

He emulated his mentor, Walter Smith, by relying on key men - the likes of Lee McCulloch, Nicky Law, Ian Black and Kenny Miller - and sticking with them come hell or high water. He went with seasoned, tried-and-tested figures over young, emerging talents. But Smith had far superior players and, crucially, he was better than McCoist at organising and motivating teams.

The football was often basic, functional and pedestrian. Rangers were usually hard to watch. Hearts have shown them up this season and if Rangers do secure promotion to the SPFL Premiership they will appear in the top flight not with some vibrant, blossoming young team, but with a group which generally too old and/or limited to mount any challenge to Celtic.

There has been no evolution of an attractive, compelling style. Players like Black, Law, Dean Shiels, David Templeton and Kris Boyd regressed after they joined Rangers, offering less than they had given their previous clubs. Losing to Alloa in the Petrofac Cup felt like yet another point of no return.

Since liquidation in 2012 McCoist has been a cornerstone for Rangers and the stress of holding his club together while he often felt under siege - not least from members of his own board - took a toll. Frankly, he occasionally looked knackered by it all. Even his resignation quickly fell into the cement mixer of Rangers' wearying internal politics.

The exact date of his departure, and exactly how much of a pay-off he gets, will make the headlines now. But no story is bigger than Ally McCoist wanting out of Rangers.