The Englishman has been linked with a return south with a string of Barclays Premier League clubs keen to lure him away in the January transfer window.
Hooper, who has banged in 17 goals for the SPL champions already this season, has so far failed to agree a new contract extension with Neil Lennon's side.
And Lisbon Lion Auld is fearful Celtic would struggle to replace if he was to walk out of Parkhead.
The Celtic legend said: "Goal scorers are always the hardest to replace and in Gary Hooper Celtic have one who they would struggle to replace him if he goes in the January window.
"Hooper has that priceless composure in front of goal that allows him to make difficult finishes look easy.
"I really hope that Celtic are able to hold onto him. The fact that the club are now in the last 16 of the Champions League and have a huge tie with Juventus could help persuade him to stay.
"He has a tremendous platform with Celtic right now and you look at how Fraser Forster has made it into the England squad on the back of what he has done with Celtic in the Champions League and hopefully that is not lost on Gary.
"But for me although there is a lot of speculation surrounding some of the other lads like Victor Wanyama, who has also not agreed a new deal, Hooper is the one we must keep at Celtic Park.
"At 24, Gary is still young enough and not in his prime yet as a striker. In my opinion he would benefit from another couple of seasons at Parkhead."
He added: "Celtic have had a great season in terms of what they have achieved in Europe this season.
"Hooper's name has been linked with a few clubs but I would ask are any of these clubs guaranteed Champions League football next season?"
Meanwhile, Celtic's home SPL match against Dundee United, which has been postponed twice, will now take place on Tuesday, January 22 with a 7.45pm kick-off.
They will play St Johnstone at McDiarmid Park on Tuesday February 19, also with a 7.45pm kick-off.