Aberdeen manager Jimmy Calderwood believes Barry Ferguson is so important to Rangers that he could be the difference in the SPL title race.Calderwood claims the one thing which separates table-topping Rangers from Old Firm rivals Celtic is that while the Hoops can cope with an injury to any of their key players, Ferguson is irreplaceable.

The Dons boss is of the opinion that the destination of the championship could come down to whether Ferguson is able to avoid injury.

Ahead of Aberdeen's trip to Ibrox on Saturday, Calderwood said: "I think Barry is still the man that makes them tick and if he stays fit then I believe it is going to be difficult for Celtic to catch Rangers.

"Barry is the most important player by a country mile at Rangers and for Scotland.

"Maybe I am being unfair to Rangers Football Club, but Barry has such a massive influence on how they play.

"I think Celtic can handle it if they lost one of their bigger players because they have more cover. Gordon Strachan has been so astute in his transfers.

"For example, if Shunsuke Nakamura can't play then Gordon has went out and bought Barry Robson. They could miss Scott Brown, but then they have got Paul Hartley or Massimo Donati.

"You can look at central defence where there is Stephen McManus, Steven Pressley if they need him, Gary Caldwell and Bobo Balde.

"The only problem they might have is left-back as they have not really got cover there. But I don't think Rangers have got somebody to replace Barry."

Calderwood first saw the potential in Ferguson when the future Scotland captain was the stand-out player for Rangers against a star-studded Bayer Leverkusen side.

It was October 1998 when a team inspired by a Ferguson went to Germany and defeated Leverkusen 2-1 in the second round of the UEFA Cup.

Calderwood was so impressed with Ferguson's sensational showing, he insisted the only time he has seen a youngster play better was when Diego Maradona scored his first goal for Argentina against Scotland at Hampden Park.

"I saw Barry when he was playing at Leverkusen and his fantastic - although Maradona at Hampden was probably a better performance when he ripped us apart," Calderwood said.

"But playing for Rangers against the likes of Ze Roberto, Barry was unbelievable."

Calderwood felt Walter Smith's return as the manager of Rangers has helped revitalise Ferguson following an unhappy time under the stewardship of previous Ibrox boss Paul Le Guen.

The Frenchman felt undermined by Ferguson, who was ultimately stripped of the captaincy and dropped when a fractious relationship between the two hit rock bottom.

However, Le Guen resigned shortly after that spat, which allowed then-Scotland manager Smith to embark on a second stint in charge of Rangers.

Smith immediately reinstated Ferguson as skipper and Calderwood believes the 30-year-old has been in fantastic form ever since.

He added: "I think Walter has been great for Barry and Barry has been great for Walter.

"Barry wasn't happy before and wasn't playing anywhere near the level everyone knows he can.

"But since Walter has come back, I think Barry has been phenomenal."

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