Goal.com

During the recent debate over whether Barcelona deserve to be regarded as the finest side of all time, few put Steaua Bucharest forward as a credible candidate. Yet the Romanian outfit went unbeaten for three years between 1986 and 1989, during which time they racked up three successive league titles – they won five on the bounce in total – and their tally of 104 games without defeat is unlikely to ever be beaten by another European club.

The quality of Anghel Iordanescu’s side, which benefited from the brilliance of a young Gheorghe Hagi, is often unfairly overlooked because of the perceived low standard of opposition they faced at home, but it has to be remembered that Steaua nearly claimed two European Cups during this period. Their remarkable domestic run was preceded by a shoot-out success over Barcelona in the 1986 tournament decider before then coming to an end just after a 4-0 defeat at the hands of a now legendary AC Milan side in the 1989 final.

AC MILAN: 58 Games (1991-93)

Of course, several members of that Rossoneri side which came of age that night at Camp Nou were still in their prime when the Italians claimed the Scudetto three years later, after a flawless Serie A campaign. Their triumph was made all the more remarkable for the fact that it had been Capello’s first season at the helm. Of course, Milan ultimately went on to retain their Italian title – even though their unbeaten run had eventually been ended by a solitary strike from Parma’s Faustino Asprilla at San Siro in March of 1993.

Their final tally stood at 58 games, which remains a staggering achievement when one considers that at the time the Italian top flight was the strongest league in world football. But, of course, having players of the quality of Marco van Basten, Ruud Gullit, Frank Rijkaard, Franco Baresi, Paolo Maldini (we could go on!) did make things a little easier ...

PORTO: 55 Games (2010-2012)

While Andre Villas-Boas’ disastrous spell in charge of Chelsea has prompted many to revise their opinions of the coach, particularly in light of the English club’s subsequent progression to the final of the Champions League under the guidance of Roberto Di Matteo, his work at Porto should not be devalued. He was responsible for assembling a Porto side which swept all before them during the 2010-11 season.

Indeed, that year the Dragoes won the Primeira Liga, the Taca de Portugal and the Europa League, defeating compatriots Braga in the final in Dublin. While Villas-Boas was lured away to Stamford Bridge last summer, Porto’s undefeated streak, which had begun during the 2009-10 season ultimately ran until January of this year, when Vitor Pereira’s men slumped to a shock 3-1 defeat away to lowly Gil Vicente.

AJAX: 52 Games (1994-96)

In terms of the aforementioned debate on the greatest teams of all time, another side that are also often ignored are Ajax’s Champions League winners of 1995. Boasting the most ridiculously-gifted crop of home-grown talent, which was perfectly complemented by the experience of Frank Rijkaard and Danny Blind and gloriously harnessed by the genius of Finland’s Jari Litmanen, Louis van Gaal’s side were arguably as close to perfection as any team can be. For one season at least.

During the 1994-95 campaign, Ajax went undefeated in both the Eredivisie – claiming what would be the second of three consecutive titles – and the Champions League, defeating AC Milan in the final. The only blemish on their near immaculate record that year was an extra-time defeat by Feyenoord in the quarter-finals of the KNVB Beker. It was recently claimed – mistakenly, as it has transpired – that it was impossible to beat Barcelona over two legs. For a season, though, it was impossible to beat Ajax over 90 minutes.

ARSENAL: 49 Games (2003-2004)

Of course, if we are talking about perfection, it would be downright offensive of us not to mention Arsenal’s ‘Invincibles’, who won the Premier League in 2004 without having a single blot on their copybook. Moreover, they did so while playing the most delicious brand of attacking football. Wonderfully marshalled at the back by Sol Campbell, their midfield was driven by the seemingly indefatigable Frenchman Patrick Vieira and given a touch of class by compatriot Robert Pires. However, it was the Gunners' forward line which was truly sublime, Thierry Henry’s partnership with Dutch maestro Dennis Bergkamp being the most intoxicating mix of pace, poise, precision and panache.

LONGEST UNDEFEATED LEAGUE RUNS IN EUROPE
Club Steaua B. FC Sheriff Celtic Levadia T. Union S.G. AC Milan Benfica Porto Ajax Arsenal	Span 1986-1989 2006-2008 1915-1917 2008-2009 1933-1935 1991-1993 1976-1978 2010-2012 1994-1996 2003-2004	Games 104 63 62 61 60 58 56 55 52 49

Agonisingly, Arsenal’s undefeated run was eventually brought to an end one game shy of a half-century, the Gunners suffering a controversial 2-0 defeat to Manchester United at Old Trafford, with a Wayne Rooney dive resulting in the penalty from which Ruud van Nistelrooy opened the scoring.

Still, there is not a side on our list who did not benefit from a dubious call or two themselves during the course of their unbeaten streaks.

In addition, it is also worth pointing out that while all of the above sides attracted their fair share of media attention for their admirable aversion to defeat, only Steaua, as the record holders, feature in the European game's all-time top five.

Indeed, second on the list are FC Sheriff Tiraspol of Moldova, after they went 63 games without a loss between 2006 and 2008.

Glasgow giants Celtic are third courtesy of their 62-game streak during World War I, while Estonians Levadia Tallinn are one place and one game further back in fourth.

Fifth place, meanwhile, is occupied by Union Saint-Gilloise. The Forest-based outfit were the dominant force in Belgium before World War II, racking up 11 domestic titles in total as well as managing to get through 60 games undefeated between 1933 and 1935.

However, the best unbeaten run in the history of the game, well, that particular accolade belongs to Asec Abidjan.

The Ivorians proved unstoppable for an incredible five-year span between 1989 and 1994, during which time they racked up 108 games without defeat.

Safe to say, then, that Juventus will not be troubling that particular record any time soon!