Pep Guardiola is obsessed with evolving his side, tinkering with players and experimenting with new formations to keep opponents guessing. Here, he started with the most unusual formation you'll see in European competition this year – although it caused his own players more problems than it did the opposition.

On paper it appeared Guardiola had pushed Philipp Lahm back to his traditional right-back position, rather than in the central midfield role he has usually played this season. From the outset, however, Lahm was playing in the centre of midfield. Who was at right-back? Well, no one was. Lahm's responsibility was to cover the right-back zone as well, a dual role the German international, who Guardiola has described as the most intelligent player he has ever worked with, was capable of playing considering Manchester United were not playing a true left-winger.

The central positioning of Bayern’s full-backs allowed the United forwards Wayne Rooney and Danny Welbeck space to break into in the channels. Illustration: Graphic

Even more intriguingly, David Alaba was playing exactly the same role on the opposite side, despite being up against Antonio Valencia, a proper winger. On the rare occasions United enjoyed spells of possession, those two shuffled back to defend the wide areas like conventional full-backs, but in possession they were simply extra midfielders, ensuring Bayern dominated the centre with something akin to a 1950s-style W-W formation, or a 2-3-2-3.

It did not work. With Bayern packing the centre of the pitch, Arjen Robben and Franck Ribéry were forced to hug the touchlines, providing width for the entire team.

This nullified the strengths of Bayern's wingers – they are most dangerous when cutting inside powerfully and shooting, but without full-backs overlapping, this became extremely difficult.

The unusual approach also played into the hands of United, who were playing on the counterattack and had oceans of space to break into, because Bayern's centre-backs had no support in wide areas. Danny Welbeck worked the channels dangerously and Wayne Rooney also found space following direct attacks.

After the sides exchanged goals to make it 1-1 on the night, and 2-2 on aggregate, Bayern's best spell of the tie came after Guardiola switched to an orthodox system. A conventional right-back, Rafinha, replaced Mario Götze – with Lahm returning to the centre of midfield.

Bayern were, by then, in a 4-2-3-1 formation, which was not really reverting to the Guardiola blueprint, but instead reverting to last season's treble-winning system of Jupp Heynckes. Thomas Müller moved higher up the pitch to grab the second goal, while Robben and Ribéry had more licence to cut inside, with the former completing the scoring.

Guardiola is unquestionably an extremely clever manager, but sometimes he can be rather too clever for his own good. Bayern Munich did not require a surprise tactical approach to defeat this mediocre Manchester United side, and this tie should not have been quite so difficult for the European champions.