The United boss, who has won the competition twice and brings a 1-0 advantage from the first leg into Tuesday's all-English encounter at Old Trafford, said he understood the Londoners' fixation as he shared it once upon a time.
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"It seems to be an obsession for them to win a European Cup, that is certainly why they signed Fernando Torres there is no question about that in my mind," the Scot told a news conference on Monday.
"The owner has very much nailed his colours to the mast in that respect. At the end of the day, it's a very difficult competition to win, all the best teams are there.
"To have an obsession to win a European Cup is stretching yourself a wee bit."
He said he used to feel the same way when United could not get past the semi-finals before he led them to a treble of the Champions League and the English league and FA Cup in 1999.
"When we did it in Barcelona it was the greatest feeling of all time and it took the monkey off my back for a bit," he said. "But it doesn't make Chelsea any more desperate than Manchester United tomorrow night, believe me."
Chelsea counterpart Carlo Ancelotti sought to put Ferguson straight, telling a news conference: "It's not an obsession, it's a dream."
United are keen not to get caught out like they did at the same stage in the competition last year when they were leading 3-0 at half-time in the second leg at home before letting Bayern Munich pull two goals back to go through 4-4 on aggregate.
"Concentration is vital, goals change games," said Ferguson.
EXTRA FRESHNESS
United will be helped by the extra freshness of first-leg goal scorer Wayne Rooney, who missed the weekend's league victory over Fulham while he served the first of a two-match ban for swearing into a television camera.
"Missing a game on Saturday has given him six days preparation for tomorrow, that could make a difference," said Ferguson.
He is also boosted by the return to form of winger Antonio Valencia, who scored on Saturday and barely looks like he missed six months with a broken ankle.
"We just couldn't wait to get him back," said Ferguson. "He's an outstanding footballer... his understanding of the game is brilliant, he has a great tactical brain, balance and power and speed, the boy has got everything."
The Scot will make a late decision on defender Rafael's fitness after the Brazilian bruised his knee in last week's first leg but was glad to otherwise have recovered from last month's injury crisis.
"He really has to do something special
