BLACKBURN boss Graeme Souness today said Damien Duff has the potential to become one of the game's all-time greats as Rovers prepare to face Chelsea this weekend.

The Republic of Ireland international became Chelsea's most expensive ever signing when he quit Rovers for the Blues in a £17million deal last summer.

Souness was desperate to hang on to his most prized asset but he always knew that Duff was ultimately destined for bigger and better things.

And now he's tipping his former protege to realise his full potential with the Premiership title contenders, as the team from down the King's Road aim to usurp Manchester United from their throne.

"Damien Duff is a super player who was always going to go on and play for one of the big boys," said Souness.

"He's got the talent to be one of the best left-sided players in the world.

"He's got the sort of talent to be as good as anyone I've ever played with or against.

"He was a very good player for us even though he was nowhere near his full potential.

"Now I hope he realises that with Chelsea.

"Great is a word which is used far too often in football these days.

"In my opinion, a great player is someone who does it at the highest level for 10 years, week-in, week-out.

"Damien certainly has the potential to be a great player but he can only truly be judged on that in seven or eight years' time."

Thankfully, Rovers won't have to face Duff tomorrow as an injury has prevented the 24-year-old from making an emotional return to Ewood.

However, Chelsea team boss Claudio Ranieri is unconcerned by the Irishman's absence, especially as he still has an expensive array of top-class replacements to call on as back-up.

Yesterday, Ranieri took his spending under Roman Abramovich to a whopping £115 million when he splashed out £10m on Charlton and England midfielder Scott Parker.

It was another powerful demonstration of the incredible spending power at the disposal of the Stamford Bridge boss.

Even with Duff, Hernan Crespo, Juan Sebastian Veron and John Terry all out of the equation tomorrow, Ranieri could still name a bench featuring the likes of Adrian Mutu and Claude Makelele, which underlines the Londoners' awesome strength in depth.

Nevertheless, their shrewd Italian coach is not about to underestimate the potential threat that Rovers pose.

Earlier in the season, the two sides shared the points when they drew 2-2 at Stamford Bridge and Ranieri learnt enough from that meeting to know that his team can not take anything for granted.

"Each side presents its own set of problems," said the Chelsea chief.

"Blackburn may have slipped a bit in recent times but they have plenty of quality in depth and it's amazing how teams will raise their games when they play us, or Arsenal, or Manchester United."