Boyd is the club's top goalscorer and has come to Rangers' rescue on several occasions this season, most notably in the CIS Insurance Cup final earlier this month.

But the striker has yet to nail down a regular place in Walter Smith's plans, with his critics suggesting he simply does not work hard enough to earn a starting berth every week.

Prso had no problems winning over the Ibrox faithful but was forced to quit Rangers through injury last summer, and he still has a few words of advice for his old strike partner.

"When I was here, I told Boydy never to leave Rangers," said Prso, who is back in Glasgow to watch Croatia's friendly against Scotland.

"He has not been at Rangers for long and he is young as well.

"I think he can really improve himself. It's just a matter of time."

Prso believes Boyd is comparable to Juventus superstar David Trezeguet.

He insisted: "When you put a ball into the box, the ball is going to go to Boydy. Even if there were 20 players in the area.

"Trezeguet has that and Boydy does as well.

"Maybe he does need to improve some of his game, such as running, defending and taking up better positions.

"But he has something other players don't have. I had a nice partnership with him. I like Boydy.

"If you keep telling players you must do this or that, putting pressure on him, then sometimes they will forget. Then he will become an ordinary player.

"It is good to try to improve just a little bit, but never forget what you do best."

Prso was a guest at Ibrox for Saturday's 2-1 win over Hibernian, in which Nacho Novo mimicked drinking a glass of wine when he scored what proved to be the winning goal.

Prso explained: "Nacho asked me what I do now and I told him that I have a nice meal on the terrace, then have a couple of glasses of wine. That's why when he scored he made the gesture about drinking."

There is little doubt Prso will crack open the vino if Rangers win this weekend's crucial Old Firm derby.

But he insists the championship champagne will be kept on ice even if they do stretch their lead over Celtic to six points with a game in hand.

He said: "I know that if Rangers do win the Celtic game, then they won't relax. You never know what will happen here because every match is hard in Scotland.

"You go to Aberdeen and it's hard, the same with Dundee United. You will struggle to win. It's impossible to relax."

As for a prediction?

"I think it will be 2-0, Boyd and Novo," he added.