Ioan Andone's side have made it a habit to upset the big teams and Manchester United might well be next.
Champions League: Cluj rewriting the book in Romania
Cluj, Romania's second biggest city, does not warrant a single mention in Behind The Curtain, the excellent 2006 book about football in Eastern Europe.
There is no room for Cluj, population 331,990, in the 25-page chapter on Romanian football which instead discusses teams from eight provincial cities alongside Steaua, Dinamo and Rapid, historically the country's best known clubs from the capital, Bucharest.
The omission was understandable. As recently as 2003, Cluj were a third division side who had spent most of their history in the second tier following their formation in 1907.
But the businessman Arpad Zoltan Paszkany, who made his money in supermarkets and construction, began investing in the club in 2002 and success followed. Cluj won the second division in 2004 and the Romanian title in 2008, 2010 and 2012.
The Romanian Cup was lifted three years in succession in 2008, 2009 and 2010 and Cluj also became European regulars, reaching the Champions League group stage for the first time in 2008, where they held Chelsea 0-0 at home following a narrow 2-1 defeat at Stamford Bridge. They entertain another English team, Manchester United, tonight.
Cluj's Dr Constantin Radulescu Stadium sits on a hill close to the centre of a city previously better known for its large student population and being a base for mountain walks.
The stadium was rundown before Cluj acquired their benefactor, and still only has three stands, but they have been completely rebuilt and it now seats 24,000.
It is a perfect venue for a club who maybe closer to Hungary and Ukraine than Bucharest, but who consistently upset the bigger capital teams.
"They're well organised on an off the field," said Gheorghe Hagi, Romania's greatest ever player and the star of the 1994 World Cup. "CFR [Cluj] did nothing when I played in the 80s and 90s, but they've been the strongest team in Romanian football in the last five years. Manchester United will be favourites, but they should not underestimate CFR."
Hagi owns Viitorul Constanta, recently promoted to the same first division after successive promotions. “Our philosophy here is to promote the best young Romanian talent,” he said. “We play CFR, who have a different philosophy which works for them.”
At Cluj, Romanians are outnumbered by foreigners: South Americans from Brazil, Argentina and Uruguay.
One of them, the Brazilian winger Rafael Bastos, scored both goals as Cluj surprised many by winning 2-0 at Braga in their opening Group H game.
The Portuguese side had a double reason to curse, they had let the man who is now the Champions League joint top scorer leave for free.
Bastos was one of three Portuguese who signed from Braga, along with the first-choice goalkeeper Mario Felgueiras and the midfielder Luis Alberto. They joined the other Portuguese players already at Cluj, who boast more first teamers from that country than Romanians, with three of the four defenders and the goalkeeper in the previous European games from Portugal.
Their coach, Ioan Andone, is unmistakably Romanian, enjoying his second spell at the club. UAE fans will recognise him from his ill-fated, four-month 2009 spell coaching Al Ahli in Dubai.
Andone won Cluj's first title in his first spell to cement his popularity.
While this will be Cluj's first ever game against a United side who will be missing Paul Scholes, Ryan Giggs, Antonio Valencia and Michael Carrick, Andone was in charge of Dinamo Bucharest when they played United in a qualifier for the 2004/05 Champions League.
He failed to defeat United then, but his side have come through two qualifying rounds to reach the group stage this season, winning all four games home and away as they beat Slovan Liberec and Basel, the Swiss side who knocked United out of last season's Champions League.
United needed two penalties to overcome Romanian champions Otelul Galati in Bucharest last year, and their recent league form has been questionable leading up to Saturday's 3-2 home defeat to Tottenham Hotspur.
Sir Alex Ferguson's side are determined to right the wrongs of their unusual Champions League failure in Europe last season, but they will face an unexpectedly tough test tonight in Transylvania.
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