The Blues need to make this one count after losing their Premier League title to United.
Chelsea finished six points behind United in the league and lost to Liverpool in the Champions League semifinals. Its consolation success in the League Cup represented a poor return on owner Roman Abramovich's preseason investment in striker Andriy Shevchenko and midfielder Michael Ballack.
Chelsea won the last FA Cup final at the old Wembley stadium in 2000, and a victory in the first at the rebuilt arena would go a long way to securing coach Jose Mourinho's job for next season and restoring some much-needed optimism to the west London club.
"I wouldn't say it is revenge because it is just a one-off game," Chelsea winger Arjen Robben said. "But it is going to be a big game with a great atmosphere and that's why we have to show the whole world how good our game can be."
And the game certainly is big.
A sellout 90,000 crowd will fill the rebuilt 800-million pound (US$1.58 billion; euro1.17 billion) Wembley to watch only the third final between the teams finishing 1-2 in the top flight of the English league.
"Games like Saturday's are the kind that you work so hard for in training every day," Manchester United defender Nemanja Vidic said. "Matches against big teams and big players on the biggest stage. It'll be great to be involved in a game that will go down in history."
The last time the top two teams met in the Cup final was in 1986 when Liverpool played Everton. If United is looking for omens, red-shirted Liverpool beat blue-clad Everton 3-1 to clinch a league and cup double.
If United adds to its record 11 FA Cup wins, it will take the double for a fourth time - more than any other team.
Chelsea, however, can draw comfort from its recent record against United. Mourinho has won five of his 10 matches against United, while United's Alex Ferguson can claim just a single victory.
This season's league meetings were both drawn, with a second-string United side holding Chelsea 0-0 at Stamford Bridge on May 9 - after the Premier League title had already been won.
The FA Cup is the only English title to have eluded Mourinho in his three years with Chelsea, with successive Premier League titles and two League Cups.
His confident demeanor has been shaken this season as player injuries, poor form and, most recently, personal troubles contributed to a disappointing campaign. This week, Mourinho attracted headlines for his arrest in an argument over his pet dog.
Defender Ricardo Carvalho, Shevchenko and Ballack are among the Chelsea players out with injuries, with left-back Ashley Cole and midfielder John Obi Mikel also in doubt. Mourinho has even made the lighthearted suggestion that third-choice goalkeeper Hilario could play as a substitute striker.
Chelsea may also be unsettled by unrest in the squad. British daily The Sun reported Friday that captain John Terry, star midfielder Frank Lampard and Robben are unhappy at being told not to expect salaries as high as those of Shevchenko and Ballack when they sign new contracts.
United will be without striker Louis Saha and captain Gary Neville, so Alan Smith may start up front and Wes Brown is likely to play at right back.
Although United has won plaudits for its attacking style, its defense will have to be on top form to hold out against Didier Drogba, who scored a league-high 20 goals.
"Drogba is a great player who has scored a lot of goals and it'll be tough to play against him," said Vidic, who will partner Rio Ferdinand in central defense. "A team isn't just about one player. It doesn't matter who plays because they have great quality. I just hope I can do my job well."
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