Charlie Nicholas has issued a warning to his former club Celtic over their pursuit of Aaron Hickey.

The ex-Hoops striker is hesitant to accept that Hickey's defensive abilities have improved in the year he has spent at Bologna and hopes his old club don't over-spend on the 19-year-old.

Ex-Hearts lad Hickey was wanted by Celts before he moved to Italy in a deal which could have been worth around £1million. Now Ange Postecoglou would have to sanction an offer around £3.5m and Nicholas reckons there are better options out there - namely Hibs' left-back Josh Doig.

Glasgow Times:

"Celtic have targeted Aaron Hickey but Josh Doig should be the standout left-back option," he wrote in his Daily Express column. "It looks as if the Hoops have identified the Bologna fulk-back. It poses the question: why didn't they buy him last summer when Hearts were selling him? Celtic didn't buy him for £1million because he was defensively weak and they were right. Hickey's strengths are going forward.

"Now all of a sudden, they look ready to pay in excess of £3million for the same player just 12 months later. He has been in Italy for a season. Has his defensive game improved? I don't really know because I have not really seen that much of him.

"That is why I would rather go for young Doig from Hibs. You can see what he has got and you can work on his defending. Maybe he has come on a lot in Italy, only time will tell if Celtic get their man."

Hickey's possible switch was not all Nicholas was concerned about. The pundit believes Postecoglou has a lot of work to do behind the scenes to improve the squad.

He does not feel Vasilis Barkas is a capable number one goalkeeper, nor does he want the Hoops to 'rely' on youngster Stephen Welsh.

But he says the club will have to splash the cash to make the necessary adjustments to wrestle the Premiership title away from Rangers. "Celtic need to spend their money on the backbone of the team," he added. "That means at least one centre back, probably two and a goalkeeper. They definitely need a new No1 because I am not convinced that Vasilis Barkas will be able to hold that jersey down.

"They need someone they can rely on and they haven't had that since Fraser Forster went back to Southampton. Ange Postecoglou also needs to add to his central defensive options. Those three signings are key to the rebuild.

"He can't wait on Christopher Jullien or rely on Stephen Welsh. He might go all the way but he needs time to find his feet and develop at Celtic. Mario Vuskovic is an interesting one from Hajduk Split. Is Postecoglou buying for the future?

"Celtic also need a right-back even though they have signed young Osaze Urhoghide from Sheffield Wednesday. Some of the potential signings certainly look interesting. It certainly looks a lot more promising than last summer when I accused the club's transfer business of being lazy."