The Blaugrana won La Liga without losing once but can they emulate the 10 clubs from Europe's top leagues to go undefeated for an entire campaign?
Getty ImagesAC Milan 1991-92
First, Arrigo Sacchi created the greatest team in club history. Then, Fabio Capello made them even better.
As star striker Marco van Basten said at the end of AC Milan's undefeated 1991-92 campaign, "perfection doesn't exist in football, but we came pretty close this season."
Their pursuit of perfection had begun in uncertainty, with Sacchi having stood down as AC Milan boss in 1991 to take charge of the national team and been replaced at the helm by former Rossoneri midfielder Capello.
The latter's only previous top-level coaching experience at San Siro had come during short spells as a caretaker and an assistant but the in-house appointment paid off spectacularly for Milan, with Capello claiming the Scudetto in his first season in charge with an undefeated record.
Capello's first Serie A loss didn't come until spring 1993, after a record-breaking run of 58 games unbeaten.
Milan retained their title that summer and then, 12 months later, made it three in a row before destroying Johann Cruyff's Barcelona 'Dream Team' in the Champions League final in Athens to strengthen their case as one of the finest sides in history.
AdvertisementGetty ImagesAjax 1994-95
Kluivert, Van der Sar, Reiziger, the De Boer twins, Davids, Seedorf, Rijkaard, Blind, Kanu, Overmars, Litmanen – in 1994, Louis van Gaal's Ajax boasted the most complementary and exciting mix of homegrown youngsters and wily veterans the game has ever seen.
They were an irresistible force, sweeping all before them in the Eredivisie and the Champions League.
PSV may have had a budding Brazilian superstar in Ronaldo but Ajax had their own teenage sensation in Kluivert, who hit 18 goals as Ajax won the Dutch title by seven points from Roda JC.
They also went unbeaten in Europe, beating title holders AC Milan not once, not twice but thrice on their way to lifting the Champions League, with Kluivert netting the only goal in a 1-0 win over the Rossoneri in the final in Vienna.
Ajax went desperately close to retaining their crown, only to lose on penalties to Juventus in the 1996 tournament decider, and that signalled the beginning of the end; the break-up of an outstanding squad.
It was a shame because as Jorge Valdano had conceded after watching Real Madrid lose 2-0 at home to Ajax in November 1995, “Ajax aren’t just the team of the 90s; they’re approaching football utopia.”
Getty ImagesArsenal 2003-04
Preston North End's double winners of 1888-89 were the first English side to go through a season undefeated but it is worth noting that they were playing in a league of just 12 teams.
Thus, Arsenal's perfect campaign in 2003-04 is slightly more impressive. Indeed, whatever one thinks of Arsene Wenger now, his 'Invincibles' will forever remain a Premier League masterpiece, unblemished and unbeatable.
Billionaire businessman Roman Abramovich had arrived in London in 2003 intent on usurping the Gunners as the capital's top club – Gunners vice-chairman David Dein quipped, "he's parked his Russian tanks on our lawn and is firing £50 notes at us" – but Arsenal decided against splashing the cash, with Jens Lehmann their most notable acquisition, at a cost of just £1.5m.
Instead, they focused their attention on retaining the services of France internationals Patrick Vieira and Robert Pires and that policy paid off, with both playing pivotal roles in the Gunners going the whole season undefeated.
They enjoyed some good fortune along the way, with Ruud van Nistelrooy missing a last-minute penalty for Manchester United at Old Trafford – which provoked a most unsavoury reaction from several Arsenal players – but, for the most part, Lehmann was fantastically well protected by Sol Campbell & Co.
Thierry Henry, though, was Arsenal's difference-maker, an attacker as elegant as he was effective. With his pace and poise, he repeatedly inspired them to victory, most notably in a rousing, come-from-behind win over Liverpool at Highbury and he was the embodiment of the team's mix of perspiration and inspiration.
As a rightly proud Wenger declared after watching his side crowned champions at the home of north London rivals Tottenham, "We've been remarkably consistent, haven't lost a game and we have played stylish football. We have entertained people who just love football."
Getty ImagesAthletic Club 1928-29 & Real Madrid 1931-32
Athletic Club were the first side to go through a Liga season undefeated, in 1929-30, although it is worth noting that only 10 teams participated.
Barcelona had won the inaugural title but they finished second, seven points behind the Basques, who won 12 of their 18 matches, scoring 63 goals along the way.
Real Madrid matched Athletic's feat in 1931-32, though, again, there were still only 10 teams in the league.
Athletic actually won more games than anyone else (11) but they suffered four defeats, whereas Madrid went unbeaten, denying the Basques a third successive title with a record of 10 wins and eight draws.
Another interesting fact is that Los Blancos were known simply as 'Madrid' at the time because, during the Second Spanish Republic, all clubs dropped Royal patronage from their names and removed any crowns from their crests.