Hooper is a top target for Norwich City this month.
Caldwell, 30, said: "If Gary believes he's good enough then the chance to move on will come again.
"The opportunity to play twice against Juventus and have a real opportunity to beat them and have four games in the Champions League knockout stages is massive.
"Footballers get a hard time with people saying it's just about the money.
"Don't get me wrong - I've played with some guys for whom it is! But 99 per cent of footballers play the game because they love it.
"To have that chance of playing Juventus home and away and get to the quarter-finals of the European Cup, a stage 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."