Former Chelsea captain Marcel Desailly says Michael Essien could be the key to the Blues' Champions League hopes.
Essien moved to Chelsea from Lyon in August 2005
Essien, 24, struggled to adapt after joining Chelsea from Lyon in 2005, but is now justifying his £24m price tag.
"He has been one of Chelsea's best players this season despite not playing in his best position.
"He is powerful, intelligent and good technically - all the qualities you need to do well in the Champions League," Desailly told BBC Sport.
"Essien wasn't yet a top player when he arrived. Lyon is a big club, but it's not Milan, Barcelona or Chelsea," he added.
"But the quality was there and has come through. He's been fantastic."
Ghanaian Essien has mainly been used on the right side of a midfield diamond this season by Chelsea manager Jose Mourinho.
Desailly, who was born in Ghana before moving to France as a child, believes Essien's best position is in the centre, but says he can still influence games from the wide position.
"When Chelsea scored their second goal against Barcelona at the Nou Camp (to draw 2-2 in October), it was Essien who was the inspiration," he said.
"He used his power to get the ball, went forward with pace and then gave the right ball."
The start of the season is always important for a new player and the luck didn't come for him
World Cup winner Desailly, who spent six years at Stamford Bridge, also urged Chelsea fans to be patient with £30m striker Andriy Shevchenko.
The Ukrainian has scored only five goals since moving to Stamford Bridge from AC Milan in the summer.
"The quality is clearly there because Shevchenko succeeded at a high level for so long with Milan," said Desailly, who made the same move from Milan to Chelsea in 1998.
"And he is not the type of player who will be scared about the speed of the Premiership.
"There are other players who have been afraid of the speed - you could see that Morientes and Crespo had a little bit of a problem there - but not Shevchenko.
"The quality of the player is so high that he will succeed. His time will come."
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Desailly said too much was expected of the 2004 European Footballer of the Year when he arrived in England.
"People expected him to come in and score goals straight away, but I knew that wouldn't happen," Desailly said.
Moving from Milan to Chelsea is not easy according to Desailly
"I made the same move and it was difficult to adjust at first.
"Every big club in Europe treats its players well, but Milan's organisation is something else. They really make you feel at home.
"And Italian and English people are very different. Italians are hot and you feel the passion more there than in England.
"Anglo-Saxon people are more distant. It's not that you are less friendly, just more reserved and distant."
Desailly thinks Shevchenko's poor start to the season - he scored just one goal in his first eight games - affected his confidence.
"The start of the season is always important for a new player and the luck didn't come for him," he said.
"When the luck is not there you lose confidence and confidence is one of the most important things for a footballer.
"Maybe he has been trying to do so well that he's been trying too hard in training and matches.
"He needs time. It's just a question of confidence and understanding how he plays and how he fits into the team a little more."
Desailly currently works for French television and is an ambassador for the Laureus Sport for Good Foundation.
He also supports an orphanage of 140 children in Ghana.