Legend Ferguson couldn't believe Bielsa's Man Utd preparation before famous win

The 2011-12 season was an annus horribilis for Manchester United for a number of reasons.

However, amid all the drama of Sergio Aguero delivering Manchester City the Premier League title at the eleventh hour, Sir Alex Ferguson's other big humbling often gets forgotten.

United's European exits under Ferguson after their last Champions League triumph fell into a few distinct categories, from honorable defeats against unstoppable Barcelona sides to the relative self-sabotage against Bayern Munich in 2010 and Real Madrid three years later.

In the midst of all that, though, we had something Fergie's United weren't used to facing: a comprehensive defeat against a team they were expected to beat, after being caught by surprise.

Marcelo Bielsa was their conqueror on that occasion, returning after more than a decade out of club football to beat the Premier League holders home and away and force Europe to take notice.

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Bielsa arrived in Bilbao off the back of a spell in Chile which saw the South Americans light up the World Cup with the kind of football which has made him popular with plenty of fanbases.

Not only did La Roja make the 2010 World Cup after missing the two previous editions, but they made it out of a tough group before falling to Brazil in the last 16.

Athletic had secured a solid enough sixth place finish under Joaquin Caparros the previous season, but a change of president was followed by a change in manager, leaving Bielsa in position to build on what his predecessor had left behind.

At home, that meant a steady league campaign and a run to the Copa del Rey final, while there was plenty more at play on the continent.

After winning their Europa League group, Athletic needed goals from teenager Iker Muniain to make it through the first knockout round and set up a meeting with the reigning Premier League champions.

United themselves were very much in the mix domestically, but it was a different story in Europe as defeat away to Basel in their final group game saw the Swiss side make Champions League progress at their expense.

Ajax were eliminated in the first knockout round, despite the Dutch side almost clawing back a three-goal deficit, and the warning signs were there as Ferguson's men prepared to take on their Basque opponents. Ultimately, though, United ignored the signs and suffered as a result.

Before the first leg, United were given a guide to the task they would face when their former striker Carlos Tevez spoke effusively about Bielsa.

"I think Ferguson and Bielsa are the best managers," Tevez - who won Olympic gold under his compatriot in 2004 - told Fox Sports Latin America.

"I know Ferguson didn't have the best relationship with me but together with Bielsa, those two are the best managers I had."

For the first 40 or so minutes at Old Trafford, Ferguson was winning the debate. Wayne Rooney put the hosts ahead, mopping up after Gorka Iraizoz could only palm a Chicharito shot into the England forward's path, though United were lucky to stay in front as Markel Susaeta's lob beat David de Gea but dropped just wide.

That luck would eventually run out moments before the break, though, with Fernando Llorente arriving late to head the visitors level, and things only got better for Bielsa's side from there on out.

Leeds fans will be very familiar with the relentless attacking play of Bielsa teams, regardless of the scoreline, and the second half at Old Trafford was the kind of one-way traffic you get when that goes to plan.

De Gea produced three big saves to keep the scores level, including a fingertip stop to deny Muniain, but even he was helpless when Oscar de Marcos ran onto a sumptuous scooped ball from Ander Herrera and found the corner.

Two became three in the final minute, Muniain beating De Gea to the rebound after the keeper parried away a shot from substitute Gaizka Toquero, and Wayne Rooney's stoppage-time penalty wasn't enough to prevent United travelling to San Mames needing to win to prolong their European run.

This was still Fergie's United, though, and no one was writing off a team who had played nine European games and scored in the final 10 minutes of six of them.

The issue, however, was that Athletic still had plenty in the tank.

After hitting the post inside the opening 15 minutes of the return leg, Bielsa cut a frustrated figure, perhaps aware that his team wouldn't get too many better chances. But while others might have been prompted to protect what they held, the Argentine continued to usher his side forward.

The reward came just 10 minutes later, and the goal from Llorente was the best of the bunch.

Watching a long diagonal ball from Fernando Amorebieta all the way, the striker hit a first-time volley which arrowed across De Gea and found the bottom corner. Looking back now, it feels like an early prototype of the goal Robin van Persie scored for United against Aston Villa the following season, the kind of strike that belongs to a player who trusts his own abilities to the fullest.

It would be Llorente's last major contribution of the night, with injury forcing him off before half-time, but that didn't change Athletic's approach.

The hosts were showboating in a way which didn't even feel disrespectful - it just looked like a team playing the only way they knew how.

First, defender Andoni Iraola waltzed through the United defence and slotted wide, but he and his teammates wouldn't need to wait much longer for their second goal.

Iraola was involved again, starting the move with some sharp play down the right, but it was De Marcos who finished it with a deflected effort.

In truth, it should have been more, with Toquero the most wasteful member of the dynamic front-line. And yet, even after Rooney pulled one back from long range, there was no real sense that Athletic would pay for their profligacy.

"[Ferguson] gave me praise that I never forgot," Bielsa would later say. "He said he wasn't surprised that Athletic had won.

"He also said he wasn't surprised how much our team ran to be on equal terms with them.

"What did surprise him was on the day of the game, in the morning, my team had trained for an hour-and-a-half.

"I never forgot that comment from him.

"There is something that justifies training on the day of the game. Of course, the training consumes some energy that would be needed in the game.

"But that training session showed the players where to run, it co-ordinated them.

"That allowed them to run less in the game because they were in the correct positions."

There were moments in both legs where it looked as though the two teams were playing a different game, such was the space afforded to Athletic whenever they got near United's box.

That's not the sort of thing that happened to Ferguson's teams all that much, either at home or on the continent, but this was no fluke.

United had beaten themselves under Ferguson, and been beaten by the best while the Scot was in charge, but few if any took them apart as comprehensively as Bielsa's Athletic.