At 4 p.m. west London time tomorrow, two cultures will collide. As they say on the fireworks, stand well back. From the north comes youth, Britishness, faith in the virtues of hard work on the pitch and prudence off it.
Waiting in the south will be experience, foreigness, faith in the beautiful game and extravagance in the transfer market.
Forget the stereotype. Once Chelsea park their Ferraris, polish off their pasta and drop off their dolly birds, and once Leeds United hang up their flat caps and re-cage the ferrets, two distinct footballing philosophies will take to the hustings. Football is about to debate its own version of the north-south divide.
David O'Leary (41), in his first stint as manager, is a soft Irishman with a hard centre. "He possesses a `nasty streak'," says one of his starlets, Harry Kewell.
"If they let me down they know they'll have their knees cut off, big time," O'Leary once said of his young team.
Tutored in the George Graham school of pragmatism, O'Leary spends carefully in the transfer market and has been brave enough to give youth its head, just as Graham did at Arsenal to produce two title-winning sides.
Top of the Premiership, still in the FA and UEFA Cups, O'Leary keeps insisting: "I'm naive and I'm learning. I'm the baby of Premiership managers." But his is a side with a future.
Gianluca Vialli (35) and often too nice for his own good, was fashioned in the more cosmopolitan classrooms of Serie A. His is a side with a great past. But he too likes playing the manager with an L plate.
"I haven't got a great experience," argues the Italian, "so I think I make more mistakes than, say, Alex Ferguson." This is a man who this season fashioned Champions League draws at Milan and Lazio.
Those abilities, however, will be tested fully tomorrow, for not only are Leeds the opponents, but Vialli's Blues are back up against their bete noir, the Premiership.
A 4-1 defeat at Sunderland followed by that 0-0 draw at Lazio tells its own story of where Chelsea's tactical preferences lie. Europe offers them space, the Premiership only claustrophobia - and a man up your backside the whole game. Starting tomorrow Desailly, LeBoeuf, Petrescu, Deschamps, Zola - feted and experienced players though they are - urgently need to stop treating the domestic pressing game as too stifling, too sweaty, too native for broadened minds.
Michael Duberry used to play for Chelsea. He now plays for Leeds. And he issues a warning: "Chelsea gell together so well in European games because they all have experience of playing at the top level in Europe. They know what to expect and how to cope with it.
"But we're not a team that can sit back and let sides attack us. In Europe, for instance, a lot of teams want time and space. But we deny them both.
"We have far more home-spun players than Chelsea but we show the English spirit by working hard for each other, when someone makes a mistake there is always someone there to correct it. We have the will to do well." While the current Leeds side contains five English players and only three not from England or Ireland, Dennis Wise flies the lone union flag in the Chelsea first team. Does this make a difference? In the Premiership, seemingly so.
In terms of the result, Chelsea desperately need a win to maintain their fading hopes of rejoining the title race. Leeds face yet another demanding test of their ability to stay the course.
O'Leary reached almost immediately into the cradle when he took over from Graham at Elland Road in October 1998. In the Leeds side that lost to Leicester on Wednesday eight players were under 22 - Gary Kelly, Jonathan Woodgate, Ian Harte, Eirik Bakke, Lee Bowyer, Stephen McPhail, Michael Bridges and Harry Kewell. Prodigous talents all.
It was a youth policy which reaped the instant dividend of exciting, vigorous brand of football. But the fixture list's heavy workload is beginning to take its toll on Leeds' young legs. Spartak Moscow in the UEFA Cup on Thursday, Port Vale in the FA Cup on Sunday, Leicester in the League Cup on Wednesday and Chelsea in the league tomorrow. It was no coincidence that O'Leary's sprogs only triumphed in their last two league games, both against lowly opponents, Southampton and Derby, thanks to injury-time goals, the latter hotly disputed.
Defeat by Leicester further smacked of the fatigue which O'Leary insists will ultimately prevent his fledglings winning the title - this year anyway.
The Irishman holds the key to a transfer war chest of £30 million with which he could easily freshen his battered squad. But, echoing his mentor's voice at Tottenham last week, and in defiance of Vialli's £10 million splurge on Chris Sutton, he refuses. "You won't find me going for short-term measures," he insists.
"It would help no end if we could get a few new players in but that is easier said than done. I could go out and blow a few million tomorrow but I won't spend as much as a penny on the wrong people. There is a shortage of quality players out there."
Perhaps he had his fingers burned with Danny Mills, a £4.5 million summer signing from Charlton who is yet to warrant his fee. And questions still remain about why O'Leary bought Darren Huckerby and not the younger, more promising Robbie Keane. Chelsea are similarly burdened by a squad lacking the quality in depth of the yardstick, Manchester United.
At the Stamford Bridge nursing home just three of Chelsea's first team are under 30 and with so few quality youngsters coming through the ranks, Vialli will need to buy virtually a whole new team soon, with all the bedding in problems which that presents. But tomorrow is about the present. So let us finally toss one more ingredient into our pot which promises to aid the explosion.
In 1970 Chelsea won an Xrated FA Cup final replay against Leeds. The rivalry has rarely cooled. The season before last, a bruising league game between the pair saw two Leeds players sent off before half-time. Last season the embers of hostility were reignited when no fewer than 13 yellow cards were shown in the match at Elland Road. Frank LeBoeuf also received his marching orders.
All in all, it promises to be quite an afternoon.
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