Hoops assistant boss Johan Mjallby admits that, if the south coast club – who had a £5m bid knocked back in January – do return dangling this kind of money, it will leave the Celtic board with a huge decision to make.
The 24-year-old striker still has two years of his contract to run at Parkhead, so the ball is very much in Celtic's court. However, it would be a massive profit on the £2.4m the club paid Scunthorpe in 2010 for the man who has scored 23 goals this season after hitting the net 22 times in his debut year.
But manager Neil Lennon is determined to hold on to Hooper, who is due to hold talks on a new contract when the season ends. And assistant Mjallby is keeping his fingers crossed the striker will still be here to help fire Celtic into the Champions League and defend the SPL title.
However, he did concede it would be a massive test of the club's resolve if Southampton do return with a mega-money offer.
Mjallby said: "If someone is coming in with a bid of £7m for Gary that's going to give the board and Neil some headache, in a way.
"We are delighted with him. We feel he has been tremendous for us in these last two seasons.
"But, I can't really answer that question. I know it is going to be something for the board, the chief executive and Neil to work it out."
Southampton are managed by Hooper's former boss at Scunthorpe, Nigel Adkins, and Mjallby expects the Hoops to sit down with the man who captained the side for the first time at the weekend to discuss any developments which arise.
He said: "Probably after the last game, if it is a proper offer and they are really, really ready to get him for that kind of money, then it is down to Gary how much he wants to stay here.
"We hope Champions League football is going to be something for him to look forward to, to try to improve even more.
"He has been very, very good for us during his stay here."
The attraction of testing yourself in the Premiership is acknowledged by Mjallby, however, who admitted: "Yes, I can understand the lure of it, especially if you are English and they really, really want you down there and you can show what you are all about. But, right now, he is our player, and we are delighted with him."
Whatever develops, Mjallby insists no-one should lose sight of the fact Hooper remains under contract until 2014.
He said: "Exactly ...whatever the offer is going to be, it's going to be a question for Neil, the board and the chief executive."
Meanwhile, Lennon is awaiting news on an injury sustained by Bosman signing Jaroslaw Fojut.
"The centre-back limped out of the weekend draw with Gdansk and has had his right knee scanned. Slask Wroclaw's medical team fear he could have torn ligaments.