If, as expected, Celtic clinch the league title for the fifth consecutive season in the next few weeks, few would begrudge Ronny Deila one final Roar in front of the Celtic fans.

The fist-pumping celebration and salute has become a symbol of the Norwegian's tenure at Celtic Park, a demonstration of his personality and his desire to become one with the biggest club he has found himself at in 24 years in football.

If Deila is granted that one last celebration, it'll also be a farewell, with the 40-year-old now set to leave his post at the end of the season.

The departure, almost inevitable following Celtic's Scottish Cup defeat to Rangers last Sunday, will leave the club's fans pondering the disappointments of the last two years and wondering who can put them back on a progressive track.

When Deila was announced as Neil Lennon's successor in 2014, the appointment was surprising and intriguing. A relative unknown on the European stage, the young manager had steadily improved Stromsgodset until they were champions of Norway.

The signing looked to be in line with Celtic's transfer strategy at the time. Identify a young talent operating outside the big leagues and offer him a platform to develop, along with the added bonus of European football. As a managerial Virgil van Dijk or Victor Wanyama, his success wouldn't be measured in a transfer fee a couple of years down the line but in silverware and, hopefully, continental adventure.

While not being a household name, Deila's words of introduction would have been well-received in any Celtic-supporting home.

"I want to play offensive football, keep possession and create chances," he said.

"We are going to give the fans entertaining football. We're here to win trophies and develop players. It's a fantastic step for me, the right step, and I feel very comfortable here already."

As is the way at Celtic these days, one of the toughest tests came first and the Champions League qualification campaign dealt Deila some early blows. A comprehensive defeat to Legia Warsaw was damaging but when the rulebook handed his side a reprieve, Celtic were knocked out by Maribor and any notion the new man could hit the ground running was lost.

It was a bump back to Earth for a man who had been compared to Jurgen Klopp upon arrival in Glasgow but far from damaging in the long term. Deila's plan for high-intensity football was never going to be implemented overnight and with the consolation of a Europa League place, he still had every opportunity to prove himself.

While there plenty time to produce results, there was little to work on the training ground to implement the cultural change that had been hinted at.

European football, international dates and the League Cup meant it was December before Deila had a week on the training ground with his players between matches.

Results did improve and while the Europa League group stage still didn't bring stellar performances, it did produce enough points to set up a romantic tie with Inter Milan in the last 32.

Those encounters, where a pulsating 3-3 draw at Celtic Park was followed by a 1-0 defeat in Milan after Virgil van Dijk was red-carded, gave the sense that Deila was making progress. Though the Italian side was not peak vintage, it had a significantly higher budget than Celtic and could be taken as a measure that given time, Deila could produce a team capable of making some impact in Europe.

The Norwegian's supporters took further encouragement when video of a TED-style talk given by Deila in early 2014 surfaced. The speech gave a revealing insight into the manager's mindset and dedication to team building through loyalty, respect and encouragement.

Victories over Rangers and Dundee United ensured Deila's first piece of silverware in Scotland as attention turned to the prospect of a domestic treble, an achievement more than difficult than it looks even for teams with significant resources.

That dream fell apart at a Hampden semi-final where Inverness Caledonian Thistle won 3-2 but post-match attention focused on match officials missing a clear handball by Josh Meekings in the box when Celtic were 1-0 ahead.

Despite Aberdeen's dogged fight in the league, the Premiership crown was secured by 17 points and so the first year ended with pass marks from some and scepticism from others who remained unconvinced over signs of progress in terms of style, fitness or transfer dealings. There would be no such allowance made next time around.

The Champions League qualifiers were to be the testing ground once more and yet again Deila failed in the key battle ground. After progressing past minnows Stjarnan and Qarabag, Malmo stood between Celtic and the group stages.

A 3-2 home win (with Celtic flop Jo Inge Berget scoring twice for the visitors) put the tie in the balance but in Sweden, the wheels fell off as Malmo won 2-0. Deila had no excuses as he described his side as "frightened and scared" in defeat.

Having admitted the mental block, it was down to the manager to repair the damage in time for a rewarding Europa League but, unlike in his first season, the second tier competition was not forgiving . Having drawn Ajax, Fenerbahce and Molde, there might have been some sympathy forthcoming if the Dutch or Turkish side had taken the plaudits. As it was Molde topped the group, defeating Celtic twice along the way and exposing Deila's team as under-performers on the big occasion once again.

The fourth (or fifth) European competition exit in two seasons was the beginning of the end for Deila. To be outshone by Malmo and Molde was particularly galling, both Scandinavian sides showing the tactical maturity and attitude to punch above their weight in the way that Deila's appointment was supposed to deliver for Celtic.

Again, the manager would turn his attention, his hopes and his talk to Scotland's trio of trophies but there was already a sense that he would have to do something remarkable to earn a third shot at guiding his team to the top table in Europe. The fact that people were asking if Celtic would sack a Treble-winning manager was proof that for many the possibility existed.

The accusation that Deila's side were capab le when playing without pressure but crumbled on the big occasion was given strength in the League Cup semi-final. Fresh off the back of an 8-1 demolition of Hamilton and a 3-1 win over St Johnstone, they met Ross County at Hampden as firm favourites to continue on the road to defending their trophy. After one minute, they were 1-0 up, by the 94th they had lost 3-1.

The fact that in three league games this season, Celtic defeated Ross County three times with an aggregate score of 8-1 only enhanced the perception that Deila's side struggled with occasion as much as opposition and after numerous matches to build that theory there would be one conclusive event to come.

In the long, long build-up to the Scottish Cup semi-final clash with Rangers, Deila was relaxed and confident while his opposite number Mark Warburton was quizzed on whether he could handle the pressure of the big derby.

In his final pre-match media conference Deila was all smiles, any nerves well hidden as he gently reminded people that Rangers may be the best of the second tier but his side were the best in the country.

Over 120 minutes they looked anything but and while the history books will show that it was a single penalty that marked the difference between success and failure, the performance was far from the level that the Norwegian had talked about achieving for nearly two years in Glasgow.

For a manager who talked about progress, there was nowhere left to go and the news that he wouldn't see another Old Firm game from the Celtic dugout came as no surprise.

The league is still there to be won and Celtic are in pole position. Anyone who believes that completing the course ahead of Aberdeen is no real achievement would do well to look at the English Premier League this season for signs of what complacency achieves. However, if all goes according to plan at Celtic, Deila's house warming present to whoever follows in his footsteps will be a shot at the Champions League.

His parting gift to the support is likely to be a third trophy in two years and one last reminder of a Roar that was rarely seen when it was needed most.