Ange Postecoglou once said that he liked to sign players who had a point to prove. This is something that Celtic has a decent history of...
When you think back to the team assembled by Tommy Burns, how could you not fondly remember the Portuguese goal-machine, Jorge Cadete? The fans' favourite went on to score an impressive 38 goals in 49 appearances during his all-too fleeting stay in Glasgow, but only after his career had stalled at Sporting Lisbon.
Wim Jansen's team who stopped the ten was spearheaded by a certain Henrik Larsson, who could only muster 43 goals in four seasons with Feyenoord.
And Martin O'Neill's side included pivotal players like Chris Sutton and Alan Thompson, whose careers in English football had gone off-piste.
In recent times, we've developed a useful habit of revitalising the careers of goalkeepers, none more so than Kasper Schmeichel, whose recent appearance on The Overlap revealed that he regretted leaving the English game for spells in French and Belgian football.
But this is not a new phenomenon, as Kasper is the fourth in a series of keepers who have rediscovered their mojo at Celtic Park.
Craig Gordon
Craig Gordon was seen as damaged goods after a number of injuries suffered at Sunderland forced him out of the game for two years.
His time in the wilderness made Gordon consider coaching before being snapped up by Ronny Deila in 2014.
Gordon was tasked with taking over from Fraser Forster, who had made the switch to Southampton after setting a new British record for clean sheets. It was a case of Celtic losing a £10m England international and replacing him with a free agent who had played one game of professional football in three seasons.
It was, however, a Lazarus-like comeback from obscurity for Gordon, who eventually regained his Scotland jersey. Having been stuck on 40 caps, he made his first international appearance in four years when he came on against England, of all nations.
In six seasons at Celtic, Gordon never lost a league title. He was part of Brendan Rodgers' invincible treble, and who could forget the sight of him on his knees at the final whistle after Celtic defeated Aberdeen in dramatic fashion to win the 2017 Scottish Cup?
By the time Celtic were wrapping up a quadruple treble, Craig Gordon was on the losing side as Hearts' goalkeeper in the 2020 Scottish Cup final.
Fraser Forster
Following the departure of Brendan Rodgers, Neil Lennon steadied the ship and led Celtic to a league title and Scottish Cup to complete the treble in 2018/19.
Lennon was then given the manager's position permanently and went about stamping his identity on the side with the permanent arrivals of Christopher Jullien, Boli Bolingoli, Hatem Abd Elhamed, Greg Taylor, and a little-known wing-back from the Manchester City Academy by the name of Jeremie Frimpong.
Also, on loan, in came Mohamed Elyounoussi, Moritz Bauer, and the returning Fraser Forster, who had enjoyed three previous spells at the club under Neil Lennon, albeit two of those had been back-to-back season-long loans.
By the time that he signed for Celtic for a fourth time, Fraser Forster had been cast aside by Southampton and had lost his place in the England squad. The colossus once named 'La Gran Muralla' needed a boost of confidence to get his career back on track, and his loan spell at Celtic provided him with just the tonic.
To add to that iconic performance against Barcelona that had the Spanish media swooning back in 2012, Forster enhanced his reputation further with a monstrous performance against Lazio in the Europa League and a League Cup-winning performance against Rangers in 2019.
Many felt it inevitable that Forster would extend his stay for Celtic's tilt at ten-in-a-row, but he returned to Southampton after his loan ended, leaving us wondering what might have been.
Joe Hart
Joe Hart called an end to his playing career at the end of last season, and his first and only campaign under Brendan Rodgers was arguably his finest in a Celtic jersey.
His performances, especially in Europe, had previously come under scrutiny, but he made a number of big saves during his second Champions League campaign for Celtic as he bowed out on a professional career that spanned 21 years.
Hart had enjoyed an illustrious career by the time he landed in Glasgow. He won every domestic honour for Manchester City and represented his country at the finals of four major tournaments. But the arrival of Pep Guardiola meant the end of Hart's time in Manchester and so began a nomadic five seasons at Torino, West Ham, Burnley and Tottenham.
Hart won nothing with those four clubs and it looked like his hugely successful football journey was teetering out with a whimper. That's when Celtic came in.
Not only was Hart a winner at Celtic (totting up two doubles and a treble in three years) but he also became a fans' favourite during his time in Glasgow. The 37-year-old has publicly acknowledged how touched he was when The Green Brigade paid tribute to him in their own inimitable style, and he was always going to be a hard act to follow.
Enter Kasper Schmeichel...
James McKenzie