Carlo Ancelotti must solve the riddle of 50-million-pound misfit Fernando Torres as his Chelsea side bids to overturn its Champions League quarterfinal first-leg defeat against Manchester United at Old Trafford here on Tuesday.

When the Londoners smashed the British transfer record to land Torres in January, the move was viewed as a clear statement that the club saw the Spaniard as the key to achieving Champions League success.

But a staggering 648 minutes of playing time later, Torres is yet to open his account for his new club, and his arrival has disrupted the established striking partnership of Didier Drogba and Nicolas Anelka.

In last week's first leg at Stamford Bridge, won 1-0 by United thanks to a Wayne Rooney goal, Ancelotti began with Drogba and Torres in tandem.

Yet the partnership never once looked like producing the goods for Chelsea, and the damning post-match statistic that the two players had connected for only five passes spoke volumes.

Moreover, Ancelotti's decision to substitute Drogba - who had looked by far the more dangerous of the duo - instead of Torres, has fuelled the theory that the Chelsea coach dare not omit owner Roman Abramovich's record acquisition.

The fact that Ancelotti left Torres on the bench for the 1-0 victory against Wigan on Saturday suggests he plans to start the former Liverpool striker against United on Tuesday.

Ancelotti has so far refused to confirm whether Torres will start at Old Trafford, where the prize for the victors will most likely be a semi-final against Bundesliga side Schalke 04.

"Maybe he will score the most important goal of our season at Old Trafford, who knows," Ancelotti said. "But I do not know who is in the side yet."

Ancelotti insists however that form will be the principal criteria for deciding his starting line-up.

"This is my job. I have to choose the players, not comparing the players with what money the club paid for them."

Chelsea captain John Terry added that the squad was squarely behind Torres.

"It's just a case of getting that first goal, getting that off your shoulders, and then you can move on," he said. "It must be hard as well, people carrying on talking about it.

"It must be a big weight to carry as well with the fee that he came for. But he knows he's good enough to play, the players certainly know he's good enough, and he's got our full support."

As well as effectively ending any chance Chelsea has of winning a trophy this season, elimination from the Champions League on Tuesday may well trigger a summer of upheaval at Stamford Bridge.

Ancelotti's position will come under intense pressure while British media reports have suggested that several pillars of Chelsea's success of the past decade may be on the way out.

Drogba, Frank Lampard, Michael Essien, Florent Malouda and John Obi Mikel have all been linked with possible departures as Abramovich prepares to bankroll a rebuilding of the first-team squad.

Although Chelsea will be encouraged by the memory of last season's 2-1 win at Old Trafford in the Premier League, the odds, and history, remain stacked against Ancelotti's men.

Only twice before in Champions League history has a team prevailed in a knockout tie after losing a first-leg match at home. United has also never lost a European tie after winning the first leg away.

United manager Sir Alex Ferguson can also call on a squad that is getting back to full strength, with Rio Ferdinand making a successful return from injury in the first leg to resume his formidable central defensive partnership with Nemanja Vidic.

Rooney, controversially banned for two Premier League matches last week, will also be available and itching to prove a point.

Ferguson's biggest concern following Saturday's routine 2-0 win over Fulham appeared to be the unusually quiet Old Trafford crowd, who he called on to rediscover their voices in time for Tuesday.

"The fans were quiet, they were sunbathing," Ferguson said. "Maybe they were saving their voices for Tuesday. They'd better be."