The Blues' 1-1 stalemate on Saturday has seen Carlo Ancelotti's title holders cast 11 points adrift of pacesetters United, who mounted a stunning 4-2 comeback victory against West Ham United. Sir Alex Ferguson's men hold a mountainous domestic advantage, though any triumphant thoughts can be instantly drowned out if Chelsea can reach the European pinnacle by season's end.
Throughout a campaign full of majestic highs and despondent lows, the repeated mantra has been that the Champions League is the real focus. If the club can beat the habit of a lifetime and finally be declared the greatest on the continent, manager Ancelotti's travails on the home front will be forgotten and forgiven by demanding owner Roman Abramovich.
A big improvement has to be made on Saturday's lukewarm efforts. Bar the resurgent goalscorer Didier Drogba, few Chelsea players could have come off the park saying they were at their silverware-winning best.
Captain John Terry looked occasionally error-prone against Kenwyne Jones, Frank Lampard did little but produce two fumbled saves from Asmir Begovic, and Michael Essien was outshone in the middle by the pedestrian talents of Rory Delap and Glenn Whelan. Although no Chelsea player other than error-prone Jose Bosingwa could be highlighted as having a poor game, none strained every sinew to get the three points.
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The fire for the domestic fight no longer burns as brightly at Stamford Bridge as it does for their impending European rivals.
This difference in attitude has been evident since the dominant autumn performances turned into Chelsea's winter of discontent. Sights have been set elsewhere to a competition with a May date with destiny at Wembley.
Ancelotti in his second season in English football has certainly failed to motivate his players for the day-to-day struggle. He will hope that the big occasion draws the best from his charges like it did in the 2-1 win over United at Stamford Bridge that previously threatened to draw Chelsea back into the title fight.
That evening, the cup-tied David Luiz led the way as goals from the Brazilian and Lampard secured a morale-boosting victory. When they fire on all cylinders, few can go toe-to-toe with Chelsea.
This attitude has enshrined a belief within the ranks that they finally merit the main chair at Europe's top table. The insecurities in United's defence revealed by the Hammers will be ruthlessly exploited, and if Chelsea are at their best, there will be no route back.
Time is probably about to be called on the club's greatest generation of players. Starting with Wednesday's first-leg, men like Drogba will draw their last ounce of strength to fight for the one title that has eluded Abramovich since his 2003 takeover.
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