At the back of a smoke-filled pub on a crisp, sunny afternoon in Leipzig, the 20 young ultras cheer as a round of schnapps arrives at the table. Behind them on a wall hangs a pennant featuring the crests of 14 teams from the former East German Oberliga - Carl Zeiss Jena, 1.FC Magdeburg, Hansa Rostock, Dynamo Dresden.

But there's no sign of RasenBallsport Leipzig, the team currently sat second in the Bundesliga and taking German football by storm.

Brought into life in 2009 when Austrian energy drink manufacturer Red Bull purchased the playing license of a local fifth tier side, "RB" rose rapidly up the pyramid thanks to a combination of savvy recruitment, attacking football - and of course, massive investment.

On this day, they welcome third-placed TSG 1899 Hoffenheim, another club whose rise to the higher echelons of the Bundesliga is also due solely to the backing of billionaire software tycoon Dietmar Hopp.

Derided as "El Plastico" or "El Cashico," it's a fixture which many fans of more traditional clubs believe shouldn't even exist, a fixture which represents all that is wrong about over-commercialized, modern football.

Hoffenheim quickly became public enemy number one when they were promoted to the Bundesliga in 2008, but even the club mocked as "€18.99 Hoffenheim" have seemed almost tolerable in comparison to the latest perceived threat to German football's traditional elite - RasenBallsport Leipzig. Not that the ultras care.

"We understand why we're disliked,” admits 19-year-old Fabian. "If we didn't come from Leipzig, we'd hate RB too! But we are from Leipzig and we haven't had a chance to travel around the county and represent our city in the Bundesliga."

Indeed, the last East German club to play in the Bundesliga was Energie Cottbus, who were relegated in 2009. The last Leipzig representative was VfB Leipzig (now 1.FC Lokomotive Leipzig) who only won three games in 1993-94.

"We don't particularly like the fact that we've needed Red Bull to do this," continues Fabian, "but there was simply no other way for us to ever enjoy top flight football.

"We're not here to support [Red Bull owner Dietrich] Mateschitz and we're not here to promote cans of energy drink. We couldn't care less about that. We're here because we want to travel the country, represent our city and express our identity." Not everybody in Leipzig agrees.

"Everything that Red Bull does is about selling cans of energy drink," says Lokomotive Leipzig fan Matthias, 34. "The fact they do it in football and in Leipzig is irrelevant. If chess were the biggest sport in the world, they'd use that.

"This location was picked for obvious reasons - a ready-made world class stadium, a big city with an international airport and no top-flight football. The name "Leipzig" just happens to be on the road signs. But don't think that they have anything to do with this city."

The debate over whether or not RB Leipzig really represents the city's football fans will rumble on, but one thing that isn't in dispute is the quality of football on show.

Ralph Hasenhüttl's young side have impressed with their energetic, high-tempo pressing game - and they maintained their unbeaten home record here, coming from behind to inflict a first defeat of the season on the equally impressive Hoffenheim.

The visitors took the lead after 18 minutes when Andrej Kramaric and Niedem Amiri combined to execute a perfect counter-attack just moments after Oliver Baumann had saved from RB defender Willi Orban's header. Timo Werner levelled for Leipzig before the break but the game was turned on its head on the hour mark when Hoffenheim striker Sandro Wagner was shown a straight red for a dangerous lunge on Stefan Ilsanker.

Baumann performed heroics to keep out first Werner and then Poulsen but the hosts were getting closer and finally made the breakthrough via a deflected Marcel Sabitzer effort.

"Yes it's El Plastico, but you can't argue with the quality of the football," opined Hoffenheim fan Carsten, who had made the trip from southwestern Germany. "We're two very similar teams - not just in terms of our history and our owners but in our style of play. It's exciting to watch - we have that in common!"

Nevertheless, it seems doubtful that any form of commercial coalition could develop between the two sets of fans after RB supporters were attacked by Hoffenheim fans when the two sides met in Sinsheim on Matchday 1. But it hasn't put Fabian and the RB Leipzig ultras off, and they are already looking ahead to next week's trip to Borussia Dortmund - who they famously beat in Leipzig back in September.

Fabian takes another sip of beer before abruptly turning away to join in a chant growing louder and louder across the pub. "Please don't take me home, I just don't want to go to work! I want to stay here and drink all your beer, please don't ever take me home!" they sing - in English.

They're already dreaming of Europe.