Caldwell never enjoyed the goals, nor the level of popularity, which has come Hooper's way but the club did not want to lose the defender in 2010. Eventually it did, because the contract on offer to him was less attractive than the chance to move to the Barclays Premier League. For Caldwell three years ago, read Hooper now.
So far there has been none of the verbal sparring between player and club which was the case when Caldwell and Celtic parted. The defender, an articulate and independent personality, memorably said they were "kidding themselves" if they thought he would accept the terms on offer at the time. A wage worth £19,000-a-week was reported. The club would not agree to offering more, a position supported by manager Tony Mowbray, and Caldwell duly left for Wigan Athletic in the January transfer window.
The issues Caldwell faced then are pertinent to Hooper now. Hooper has rejected an improved contract – his current deal runs to the end of next season – and is wanted by at least one club in the English top flight. Norwich City have made two unsuccessful bids for him so far and Tottenham Hotspur are also said to be interested.
Hooper has done nothing to suggest he does not want to stay with Celtic for their remaining Champions League matches and the rest of this season, but the rejection of the new contract amounts to persuasive evidence that he will move in the summer.
Caldwell was asked, yesterday, if there was anything Celtic could realistically do once a player of Hooper's potential had made up his mind to leave? "Probably not, no," he said. "The Premier League has the money, the biggest players, the biggest teams and once a player has made his mind up it's very difficult to change it. But Celtic really understand that and they are doing really well and progressing in the Champions League.
"Is there any point throwing money at Gary Hooper if he wants away? I don't think so, no. He'll move on and they'll get a lot of money for him and they'll use it to get someone hungry to prove himself up here like Gary did. Clubs move on when they lose players. It's three years this window since I left Celtic and the players and the whole club is completely different to when I left. Football moves on so quickly these days.
"Celtic is a great club but they play in the SPL and you are not playing against Manchester United, Chelsea and Arsenal and Liverpool week in, week out. Inevitably players want to test themselves at a higher level. But this window Celtic are in a stronger position because of the Champions League and the Juventus games. If I was a player in Gary's position then the Juventus games would be a huge pull to stay."
There has been a commonly-expressed view that Celtic will raise most money for Hooper from selling him now, and that his value would only decrease this summer because he would be four months closer to the end of his current contract. That is a natural conclusion to reach but not necessarily an accurate one. It does not take into account the possibility of Hooper playing well, and scoring, against Juventus, which would only increase his attractiveness to potential buyers. What Norwich City may be prepared to pay now – so far only around £5.5m – a larger, richer club may be willing to go beyond in the summer.
His current team-mate, Charlie Mulgrew, praised Hooper's temperament yesterday. "He's a good lad, 'Hoops'. He doesn't let it get to his head. He just gets on with his job and you have seen that in the last two games. Is he thriving on it? Maybe he is. A bid of £5m might be seen as derisory. We see 'Hoops' day in, day out. We know his quality and what he can do. And everyone sees the goals he scores. So, yeah, I think he is worth a lot more than that."
Celtic could have the benefit of Hooper in the Juventus ties without it costing them any money. The appeal of that to Hooper himself would be obvious: a couple of massive Champions League ties, the likelihood of one, two or even three domestic trophies, and then a summer move to the Barclays Premier League.
Caldwell stressed the probable attractiveness of the Juventus ties to Hooper. "Footballers get a hard time saying it's just about the money. Don't get me wrong – I have played with some guys for whom it is all about the money! But 99% of footballers play football because they love it.
"To have that chance of playing Juventus home and away and get to a stage of the quarter-finals of the European Cup that no Scottish club has ever reached in modern times would be a big pull for any footballer. It will be a difficult dilemma should the club accept a bid and Gary has a decision to make. In football I would always believe you back yourself – you don't jump at the first opportunity. If you back yourself there will be other opportunities in the future.
"I've never played against Gary but having watched him this year, in the Champions League especially, he's been very impressive. Not only his goals but his work rate, his pace, the way he leads the line. He would be a great addition to any team down in England."
INTERVIEW Caldwell understands attraction of moving to England but former club still have their own big draw, writes Michael Grant