The 23-year-old midfielder has been an enormous success at Rangers since his loan move from Fulham.

He is now only a handful of games away from being part of an historical trophy quadruple. Davis will be handed a key role in Wednesday night's UEFA Cup final against Zenit St Petersburg at the City of Manchester Stadium.

But Roberts, who was in the Rangers Legends squad that turned out for Linfield defender William Murphy's testimonial game at Windsor Park on Saturday, insists Walter Smith must 'break the bank' to hold on to Davis.

"Davis is a great player," said the former Tottenham, Chelsea and England defender.

"There are rumours he is moving to Middlesbrough for £5million or something like that. Hopefully, Walter can keep him because you must keep your best players.

"He has been a fantastic signing. I think Walter will seriously think about breaking the bank to keep him at Ibrox.

"But it's difficult to cope with the lure of the Premiership.

"Whatever money he is on at Fulham, Middlesbrough could offer him 10 or 20 grand more to get him.

"There is a lot of money in the Premiership, that's what Rangers are up against."

Roberts, who is a Sky Television regular, insists Rangers can end the season in a blaze of glory.

"Hopefully, they can round up the season with the four trophies," he added.

"I think they have a real chance. They will have no problems if it goes to penalties in the UEFA final against Zenit, that's for sure.

"Personally, I don't think it will be a classic game.

"Rangers will go there, get everyone behind the ball. Play one up front, they'll work hard and close people down. They (Rangers) have a fantastic defence.

"I watched the Fiorentina game, working for Sky. I basically couldn't see the Italians scoring – I couldn't seem them breaking Rangers down.

"They (Rangers) play a certain way in Europe, frustrating opponents.

"It will be the same on Wednesday. Zenit will have a lot of the ball, but again I can't seem them breaking Rangers down. And, I do think Rangers will win.

"I know people are saying they are tiring, but it's all in the mind.

"They have got five games left now. If they get through next Wednesday, then all of a sudden they've got the two league games – Motherwell away, which is a big game and St Mirren. Win those and they've won the league."

Roberts has wonderful memories from a fantastically successful career.

He added: "I won lots of trophies . . . two FA Cups; UEFA Cup; League Cup; Charity Shield; Scottish League; Scottish Cup; Division One with Chelsea.

"I've got great memories and wouldn't change a thing. I really enjoyed my time at Rangers. I was only there 18 months, but it was a fantastic time.

"The boys who are playing at the top today are very lucky people in terms of the financial benefits."

Roberts stresses he has no desire to enter club management, adding: "I've no aspirations of management.