Action Images via Reuters / Andrew Boyers Livepic
Sometimes, a new signing walks in the building at Parkhead and it's immediately clear that Celtic have signed something special, with Virgil van Dijk the obvious case in point.
Then-boss Neil Lennon has since admitted that he told the towering Dutchman to just "enjoy" his time in Glasgow, as he "won't be here long".
The ex-Groningen defender has since blossomed into a superstar after ending up at Liverpool via a stint at Southampton, but it was in green and white where he really came to wider attention.
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The Premiership was his playground, and so too has been the Premier League since then. He's one of the few to really thrive after leaving the Hoops behind.
Why Van Dijk remains a rare success story for Celtic sales
Over the last ten to 15 years or so, Celtic have sold on so many for marquee fees, yet that hasn't always translated into future success for those high-profile stars.
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Player Fee (add ons included) Sold To
Matt O'Riley £25m Brighton
Jota £25m Al-Ittihad
Kieran Tierney £25m Arsenal
Arne Engels £22m West Ham
Moussa Dembele £19.7m Lyon
Nicolas Kuhn £16.5m Como
Odsonne Edouard £14m Crystal Palace
Kristoffer Ajer £13.5m Brentford
Virgil van Dijk £13m Southampton
Victor Wanyama £12.5m Southampton
Arne Engels will be hoping to buck the trend this summer, having joined Championship side West Ham United for £22m, although the recent past hasn't been kind to those who once blossomed at Celtic Park.
Nicolas Kuhn has already been moved on by Como after just a year in Italy. Matt O'Riley is on the periphery at Brighton and Hove Albion. Jota ended up back in Glasgow after failed stints at Al-Ittihad and Rennes.
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Kristoffer Ajer, still on the books at Brentford, has at least enjoyed a solid period in English football, as too did Victor Wanyama, the Kenyan heading to Southampton himself prior to joining Tottenham Hotspur in 2016.
And yet, it truly is Van Dijk who is head and shoulders above the rest in terms of Celtic's notable sales of the modern era, the 35-year-old now arguably in contention to be named the Premier League's greatest ever defender.
He's won two Premier League titles and claimed the Champions League, while losing two finals, proving such a fearsome presence at the back for so long now at Anfield.
The player who bullied Premiership opposition in both boxes is still the one doing the same south of the border, with it having been clear from the off back in 2013 that Lennon and co had struck upon something special.
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In the present day, Martin O'Neill's side may have stumbled upon a similar level of talent.
Why Celtic might have found the new Van Dijk
Maybe there's a sense that if you throw enough mud at the wall, something is bound to stick eventually, yet after a string of dismal summers in terms of recruitment in Glasgow, the Parkhead hierarchy do deserve some credit for what has transpired this time around.
Yes, the failure to do more business before the LASK tie has again proved costly, while the inability to strike a late deal for Torino's Gvidas Gineitis also still stings, yet the signings that have been made certainly provide reason for optimism.
Shim Mheuka looks like a real handful, as does Haissem Hassan. Mika Baur is a real star in the making in midfield, while Kasper Hogh is the type of centre-forward this team has long been crying out for.
REUTERS/Russell Cheyne
It is Camilo Duran, however, who could well be the modern-day Van Dijk in terms of his immediate impact, the Colombian already perhaps looking too good for the Premiership amid his rampant start to the campaign.
From his pre-season debut against Sporting CP, Celtic's replacement for Daizen Maeda has been immense at the top end of the pitch, such a handful be it off the right or in a central role.
REUTERS/Russell Cheyne
He was a relative unknown quantity before joining, like Van Dijk, although it is quickly becoming clear why the 24-year-old scored five times in the Champions League for Qarabag last season.
The South American has that Maeda-style work ethic out of possession, yet his quality in front of goal and creativity is already shining through, already up to nine goals and assists in his first eight competitive games for the club.
The headline moment remains his breathtaking brace in the first leg against LASK, with Duran producing two finishes of simply sublime fashion, rifling the ball home to secure what looked like an unassailable lead for the hosts...
That had come while operating off the right, although even as a number nine he's looked sharp and deadly too, scoring three times against Falkirk and Aberdeen, while supplying the assist for Yang Hyun-jun's clincher against St Mirren last time out.
REUTERS/Russell Cheyne
In the view of O'Neill, speaking after the win against the Dons, Duran is a "really class player", having already become almost a talismanic figure in the wake of Maeda's exit. A senior Colombia call-up has been richly deserved too.
Of course, so early into his Celtic career, no one should be contemplating the prospect of a swift exit for the left-footed sensation, although like Van Dijk, supporters might just have to relish the £5.5m man while he's still here.