Leigh Griffiths was a conundrum to Ronny Deila. He started both of the manager's first two games in charge of Celtic, but then drifted to the periphery.
It seems inconceivable now that the striker might have been considered with indifference, but that is also a measure of how far he has progressed. Griffiths has matured as a footballer and scores goals with an impressive array of finishing ability, but he was always capable of technical aplomb.
His rise to prominence is measured in goals, since he has become the fastest player to notch 50 for Celtic, heading a list of predecessors that ranges from Charlie Nicholas to Henrik Larsson. It should also be assessed in terms of perseverance and commitment.
Griffiths is unabashed, and has declared that his ambition is to overhaul Larsson. He will feel as if any milestone is within reach, although his present focus is on performing the same act of persuasion on the Scotland manager Gordon Strachan as he managed with Deila.
The Norwegian initially preferred Anthony Stokes and then John Guidetti as his sole striker at Celtic. The former has moved on loan to Hibernian, after being effectively discarded, while the latter has scored seven goals in 22 appearances for Celta Vigo this season.
Following those two opening games, against KR Reykjavik, Griffiths started against Inverness on August 23 in what was essentially a second-string line-up. His next start did not come until November 27, against Red Bull Salzburg in the Europa League.
He continued to be in and out of the side until January 17, when a starting place away to Hamilton was the beginning of a prolonged spell in the team. That also coincided with Celtic's run of only two defeats in 26 domestic games.
Griffiths scored 16 goals in the second half of last season, compared to four in the opening months. He had developed physically - stronger, quicker, more stamina - but also in terms of his movement and awareness. He remains most strikingly a finisher, when his composure and accomplishment are most pronounced.
Yet it is development into a forward capable of contributing to different phases of play that has been as important as his continued prolific nature. Celtic have kept looking for an alternative style of centre-forward, one who is less inclined to hang on the shoulders of the centre-backs and look to spin into space behind the lines, but instead provide a pivot to play around.
Nadir Ciftci was signed from Dundee United, a move in the final hours of the summer transfer window for the loan signing of Steven Fletcher was unsuccessful, and Carlton Cole has arrived on a free transfer. Griffiths, though, remains irrepressible.
That is mostly a result of his own application and willingness to improve and evolve. It is also, though, a testament to Deila's management that a player who might have been disaffected has improved to such an extent.
Griffiths is quick, nimble, agile and powerful in the air and capable of finishing with both feet - his two goals against Dundee United at the weekend were both struck with his weaker right foot - and there remains the sense that further promise can be realised, since he is only 25.
At one stage, his private life might also have continued on a chaotic trajectory, but he now appears settled and fully committed to the understanding that to deliver on his potential, he needs to work hard on every aspect of his game. Goals and trophies are measures of a player's achievements, but Griffiths' rise in status at Celtic is also a triumph.
Shopping for reassurance
Hibernian have moved swiftly and decisively to strengthen their promotion bid with the signing of Stokes and the potential return to the club of Kevin Thomson, the midfielder who had been captain of Dundee before leaving Dens Park last week.
Stokes will lack match sharpness, having not appeared for Celtic since the second of his two games this season last August. Even so, and despite off-field indiscretions, he remains a player capable of flair and scoring streaks.
His arrival will fill the squad with confidence, but also push the current strikers - among them the impressive Jason Cummings - to raise their own games.
In effect, Rangers have managed the same feat. The Championship leaders are hopeful of adding the Brentford midfielder Toumani Diagouraga and the St Johnstone forward Michael O'Halloran to their squad.
Falkirk, too, have sought reinforcements, having brought their former player Conor McGrandles back to the club on loan. All three sides are comfortably clear at the top of the league, and so are vying with each other. The transfer business is an attempt to further underpin their ambitions.
The title will not be decided by these signings alone, but the competitive dynamic between the three clubs may be influenced by them. Stokes and, if he signs, O'Halloran would be the most likely to have a decisive effect.