IN time, Ronny Deila’s two years at Celtic may come to be viewed by the rest of Scottish football as The Era of Missed Opportunity.

The Norwegian was an affable, diligent chap who the history books will show delivered two league titles and one League Cup during his brief tenure at Parkhead.

If Celtic go on to clinch a history-making 10th successive championship 18 months from now then the bold Ronny can proudly – and rightly – claim he played his part.

Celtic, though, took a risk with his appointment and the subsequent lack of investment in the transfer market. They spent just £4m in his first season – half of which was splurged rather wastefully on Stefan Scepovic – while bringing in almost £12m from sales.

The following year they harvested around £14m from transfers while entrusting Deila with around £8m including the £3.5m he spent wisely on Jozo Simunovic and Ryan Christie. In his two seasons in charge, then, Celtic were net savers in the transfer market to the tune of around £14m.

It had the feel of a club doing just the bare minimum to get by, like a child riding a bike with one hand hoping not to fall off. They paid for that on the European front – Deila didn’t reach the Champions League group stage in either of his seasons in Scottish football – but, domestically, Celtic did at least extend their run of successive league titles.

They could have afforded to be bolder with Rangers still slogging their way through the lower leagues, but they got away with it.

But if the league title was ever going to leave Glasgow for the first time since 1985 then those were the seasons when it was most likely to happen. Aberdeen had their chances and the regret may sting for some time in the north-east that Derek McInnes and his players couldn’t put Celtic under greater pressure.

By the end of each season Deila and his players were able to stretch away, winning the title by first 17 and then 15 points. And that despite not winning in 12 of their 38 matches in Deila’s final year in charge.

That may be as close as anyone outwith the Old Firm comes to winning the championship for quite some time. In fact, it is hard to see anyone even finishing second for a generation or longer.

Celtic learned from the Deila experiment, acknowledged the presence of Rangers in the top division, and went back to full steam with the appointment of Brendan Rodgers. Neil Lennon has been similarly backed since returning the club.

Rangers took their time to get up and running after arriving in the Premiership in 2016 but are starting to flex their financial muscle a little now, too. They remain some way behind Celtic on that front but are now, without question, the second-best side in the country.

Depressing as it may be for the rest of the nation, we have been catapulted back to the pre-2011 era where the Old Firm duopoly seemed impervious and any challenges to their dominance were futile.

Celtic retain the upper hand in that rivalry thanks to the extra years of banking European money as well as the regular sale of players to England but they know now that the only test of their superiority will come from across the city and not from anywhere else in the country.

By the end of the season, Celtic will likely hold off Rangers by between six and 10 points. From there, the drop-off to the side in third could be as much as 30 points. The Scottish top flight has become a division once again where there are two all-conquering forces and 10 also-rans.

In truth, there is no clear candidate to be considered the third force in the country these days. As their tame and embarrassing capitulation at Ibrox last weekend demonstrated, Aberdeen have badly lost their way. That being swept aside so contemptuously by Rangers wasn’t viewed as that much of a surprise told its own story.

Kilmarnock finished third last year but that was down mainly to the miracle served up by former manager Steve Clarke. Angelo Alessio may replicate that achievement at some point in the future but it doesn’t look likely this season.

Hearts and Hibernian appear to be limping by from week to week, their managers doing just enough to free their necks from the hangman’s noose as supporters bay for their blood. Neither seems in any shape to push for a top-three finish.

Motherwell could well be the side most likely to take that berth, something that would serve as a massive feather in the cap of Stephen Robinson and his players but also as an indictment of their wealthier rivals that a club with smaller resources could outmuscle them.

Ross County, Livingston and Hamilton Accies are also in or around the top six currently when their balance sheets suggest they really ought to have no right to be there.

This season’s champions will take the crown on the 35th anniversary of the last time a team outside of Rangers and Celtic won the title. Barring another unforeseen financial meltdown from one or both of that pair, it could well be another 35 years before their vice-like grip on Scottish football is broken once again.