The oldest competition in football has significance for multi-winners Manchester United.
The FA Cup is never half empty for United
Don't tell the 40,000 Manchester United fans, the majority of whom are travelling south to London this morning, that the FA Cup does not matter. United may be close to sealing a record 19th league title and are in the Champions League semi-finals, but one game has dominated the talk among supporters in recent weeks: City at Wembley.
The world's oldest cup competition may be third in United's priorities after the Premier League and the Champions League, but today's opponents have certainly boosted its importance.
United fans have long celebrated City's inability to win a trophy since 1976 with banners and in song. Now United stand between City and success.
Reds have been chiding Blues since the draw, offering directions to Wembley and pointing out that they should not arrange to meet by the stadium's twin towers as they were demolished 11 years ago. The Reds want to halt City's progress for they would face a less formidable opponent in the final - Bolton Wanderers or Stoke City. One of the few ideas both groups of fans would agree on is that United v City is fit for a final, but one team will be eliminated today in front of 90,000 fans.
It is not just about getting one over on the Blues for the Reds. The Cup has provided United with some of their greatest moments, especially in the 1970s and 1980s. United did not win the league for 26 years between 1967 and 1993, and the cup offered salvation and silverware. Wins in 1977, 1983 and 1985 were huge events in Manchester, while Sir Alex Ferguson's first trophy - after being appointed in 1986 - was the 1990 Cup. With Ferguson's side finishing 13th in the league, that trophy bought the United manager time and calmed those who suggested he should be dismissed. They have not looked back since, while City have watched their neighbours with envy.
United's first trophy after the Second World War was the 1948 FA Cup. The first trophy after the 1958 Munich air disaster was the 1963 FA Cup. And the trophy was the only major honour won by United between 1969 and 1991.
Ask fans to remember their greatest moments supporting the team and a surprising number will choose cup wins - and their worst moment as losing the 1976 or 1979 finals. It was the same for the players.
"Scoring both goals in the 1976 FA Cup semi-final which took United to Wembley was the highlight of my career," said the former United winger Gordon Hill. "United fans took over Hillsborough and everyone was singing. It was a big deal for everyone at the club during a time when United didn't win the league. Losing the final a few weeks later was just awful."
United last reached the semi-final stage two years ago, where they lost on penalties to Everton after a goalless draw. Their line-up that day was a second string containing players like Ben Foster, Federico Macheda, Danny Welbeck and Darron Gibson. Ferguson has continued to play fringe players in this season's competition, with his defender-heavy line-up causing alarm before the quarter-final match against Arsenal at Old Trafford. But such is the importance of today's game he is likely to start with a strong side.
United, who have had to overcome Liverpool and Arsenal en route, start as favourites. Of the 41 games he has managed against City, Ferguson has won 23 and lost just seven. His record against Roberto Mancini is equally dominant, with one loss from five matches. United have far more experience of playing at Wembley, too, with eight visits since the rebuilt stadium opened in 2007.
"I hope that experience gives us an advantage," Ferguson said.
"We've been there a lot. But, in fairness, City have a lot of experienced footballers who've probably played there, too."
The Manchester clubs have only met once before at the semi-final stage and once on a neutral ground, Sheffield's Bramall Lane in the 1926 FA Cup semi-final which City won 3-0.
City have not won the FA Cup since 1969, though they appeared in the 1981 final - the last year they reached the semi-finals. United have been semi-finalists 12 times since then, winning the cup seven times.
United have won the FA Cup a record 11 times (from 18 finals), though they have lost their last two final appearances, in 2005 against Arsenal and 2007 against Chelsea. Just six of United's players have an FA Cup winner's medal.
Wayne Rooney had said: "I'm desperate to win it this year". But a ban for shouting obscenities live on TV means he will watch anxiously from the sidelines, along with his former strike partner Carlos Tevez, who is injured for City.
They will be nervy spectators, like the other 89,998.