To its critics, it is a glorified pre-season friendly, but to many it is as much a part of the footballing calendar as the FA Cup final.
The status of Sunday's Community Shield is a subject for debate, but an analysis of its history suggests that, for Manchester City and Manchester United alike, its importance will become apparent over the next nine months.
Come Sunday evening, one will have a favourable omen, while the other can console themselves with more distant history. The last four winners have gone on to take the title that season, even if only two of the previous 10 victors did.
Consider the significance of the last two Community Shields. In 2009, Carlo Ancelotti's first match as Chelsea manager ended in a penalty shoot-out triumph against United; a double-winning year duly followed. Twelve months later, the shift in the balance of power came at Wembley. The maiden win for Sir Alex Ferguson's United against Ancelotti's Chelsea was in the Community Shield. It was the first of four triumphs over nine months, pre-empting a campaign in which they would eliminate the Londoners from Europe and reclaim their league crown.
Moreover, a moment of fortune proved auspicious. When the new signing, Javier Hernandez, tripped and fell in the Chelsea penalty area, he unknowingly headed the ball in from shin height. It set the tone for a season when everything the young Mexican touched turned to goals.
Even United's tendency to prevail on penalties has proved an accurate guide: in 2007, Edwin van der Sar saved three successive spot kicks to enable them to claim the shield, and that season ended with the Dutchman blocking Nicolas Anelka's penalty in Moscow to make United Champions League winners.
If August tends to entail two heavyweights slugging it out, the history of this fixture contains some unlikely participants. First played in 1908 and known as the Charity Shield until 2002, it was not always an annual encounter between the previous season's league champions and FA Cup winners.
The Southern League - a division that lost its meaning as many of its members joined the Football League - provided one of the finalists in the early years.
Other contests included matches between amateurs and professionals either side of the First World War, and even, in 1950, a game between 11 of England's unsuccessful World Cup squad and a Canadian touring team.
As recently as 1972, it was contested by the Division 3 winners (Aston Villa) and the side who had finished fourth in the top flight, Manchester City.
There have been spells when, if the game was drawn, the trophy was allocated to each team for six months, with the result that Everton had at least a share of the spoils for four successive years in the 1980s.
Yet its standing owes much to the most infamous Charity Shield that was also the first played at Wembley Stadium.
The 1974 meeting of Leeds United and Liverpool is remembered for the premature departures of Billy Bremner and Kevin Keegan. The Leeds captain and the Liverpool striker became the first British players ever to be dismissed at the national stadium.
It was Brian Clough's first match as the Leeds manager. He was in no doubt where the blame lay.
"Billy Bremner's behaviour was absolutely scandalous, producing one of the most notorious incidents in Wembley history," he said.
"Bremner seemed intent on making Kevin Keegan's life a misery. He kicked him just about everywhere … until it became only a matter of time before a confrontation exploded. Eventually, inevitably, Keegan snapped - and they were both sent off. Keegan was a victim, not a culprit. The double dismissal was all down to Bremner.
"Keegan was an innocent party, who had been pushed beyond the limit by an opponent, who had appeared determined to eliminate him from the game one way or another."
Keegan whipped his shirt off and flung it to the ground. Bremner did likewise. Besides bringing both infamy, the repercussions were considerable. Bremner, later voted Leeds' greatest player, incurred an eight-match ban and his loss was felt. By the time he was available again, Clough's 44-day spell at Elland Road had ended with his sacking.
Liverpool's triumph, on penalties, may have appeared a footnote. It actually provided the first silverware of a golden reign under the newly-appointed Bob Paisley, whose nine years in charge produced six Division 1 titles and three European Cups.
Bremner, however, was not the last midfield enforcer who forgot to display his charitable side in the Charity Shield. The unwanted distinction of being the last player to be sent off at the old Wembley Stadium fell to a man who famously did not approach any game in a half-hearted manner.
Riled by a Jimmy Floyd Hasselbaink foul that went unpunished in 2000, Roy Keane launched into a reckless challenge on the striker's Chelsea teammate, Gustavo Poyet. "It was only the Charity Shield, but it was a nasty game," said United's uncompromising Irishman. "The media went to town on me. Why did Keane get involved, they asked. The answer is simple.
"You can't allow yourself to be the victim. If they put it up to you, try to intimidate you, to see if you've gone soft, you've got to send the signal back."
Similar sentiments were expressed by Steven Gerrard two years later.
"The Community Shield is supposedly an exhibition match to kick the season off, and it certainly did kick off," the Liverpool midfielder said. "Patrick Vieira and I have had some bruising run-ins, and this was definitely one of them.
"Wanting to stamp my authority on the game, I deliberately hit him with a hard tackle. Liverpool needed to show they were not scared of Arsenal and all their big names." His sanction was only a yellow card.
The following year, the 2003 encounter between Arsenal and United was another game that was rather too competitive. Phil Neville was booked in the first minute, while it was a surprise that the Arsenal replacement, Francis Jeffers, was the only man dismissed.
Now Ferguson argues United will use tomorrow as a fitness exercise. Yet he is innately competitive and, a nine-time winner, is its most successful manager. It is no coincidence Ryan Giggs, a victor eight times, stands alone, the most decorated footballer in the history of English club football with yet more medals to his name.
His first triumph was a curiosity. The 1993 meeting with Arsenal was decided from 12 yards when one goalkeeper, Peter Schmeichel, rifled a penalty past the other, David Seaman.
Not that United shot-stoppers' memories of such occasions are all happy. In 1967, Alex Stepney was beaten by his Tottenham Hotspur counterpart, Pat Jennings, with a goal kick that bounced over his head.
It is one candidate for the most embarrassing moment. Another occurred in 1992 when, stationed on the goal-line, Gordon Strachan had three attempts to control the ball and ended up back-heeling it into his own net. This was another memorable Leeds-Liverpool clash, but for different reasons: Eric Cantona scoring a hat-trick as Leeds triumphed 4-3.
Cantona was to go on and score in two Charity Shield wins for Manchester United. He, like other Wembley specialists such as Ian Rush and Bryan Robson, was equally effective in August. Their modern-day equivalent is Didier Drogba, whose match-winning 2005 brace was part of a theme of domination against Arsenal.
This can also be the first chance to make a point. In 1996, Alan Shearer spurned Manchester United to join his hometown club, Newcastle United, for a then world-record fee of £15m. Reprisals occurred almost immediately as Ferguson's charges hammered the big spenders 4-0.
While debuts can be deceptive - the expensive failure Andriy Shevchenko scored on his Chelsea bow in 2006 - Wembley provides the first chance to assess the newcomers. Sunday, that means United's David de Gea, Phil Jones and Ashley Young, and City's Gael Clichy, Stefan Savic and Sergio Aguero.
It is where the scrutiny begins in earnest, where judgements acquire validity and where pre-season can drop its first three letters.
It is the time to strike a psychological blow and the opportunity to lay down a marker for the year.
Richard Jolly's pick of five great Community Shield games
1911: Manchester United 8 Swindon Town 4
The fourth Charity Shield was a record breaker. The total of 12 goals is unlikely to be beaten, along with the double hat-trick of Harold Halse, the Manchester United centre-forward. Swindon, the Southern League champions, discovered the Division 1 winners played at a different level altogether.
1954: Wolverhampton Wanderers 4 West Brom 4
A Black Country derby that ranks among the greatest. Wolves led 2-0 and 4-2 but were pegged back by their local rivals. Ronnie Allen, the striker, scored a 24-minute hat-trick, including the equaliser, to ensure that Wolves and West Brom kept the trophy for six months apiece.
1967: Manchester United 3 Tottenham Hotspur 3
Best remembered as the match that contained the only goal of the great keeper Pat Jennings's long career. It was also a six-goal thriller between arguably the two most attacking teams of their era with Bobby Charlton, United's record scorer, striking twice, and Denis Law once.
1978: Nottingham Forest 5 Ipswich Town 0
Brian Clough's Forest side were to go on and conquer Europe, but they started the 1977/78 season by equalling the biggest winning margin in the Charity Shield to dismantle a fine Ipswich side. Martin O'Neill led the rout with two goals.
1992: Leeds United 4 Liverpool 3
The high point of Eric Cantona's brief Leeds career. The Frenchman scored a hat-trick, including a sublime second, and teammate Rod Wallace managed a treble of his own with three assists. Despite Gordon Strachan's comical own goal, it remains the last trophy Leeds, then the reigning champions, have won.