Sometimes tactical brilliance is about a manager devising an intelligent pre‑match plan, and sometimes it takes mid-game improvisation. This was a perfect example of the latter, with Garry Monk switching from his initial 4-2-3-1 formation to a 4-3-1-2 early in the second half, and Swansea turning a 1-0 deficit into a 2-1 victory.

On paper, it was a peculiar substitution when trying to get back into the game – a defensive midfielder, Ki Sung-yueng, replaced an attack‑minded winger in Wayne Routledge. But the knock-on effect was crucial, with Swansea exerting more control in the centre and allowing Gylfi Sigurdsson and André Ayew into advanced roles behind Bafétimbi Gomis, finding pockets of space and taking up positions United struggled to cope with.

In particular, Swansea caused problems in their right-hand channel. The change of formation meant Swansea were no longer playing with outright wingers, which encouraged Luke Shaw to bomb forward down the flank. However, Swansea’s attackers were drifting laterally into the spaces left behind, and Sigurdsson and Ayew took it in turns to move into peculiar, inside-right positions between Shaw, the left-sided centre-back, Daley Blind, and the left-centre midfielder, Bastian Schweinsteiger. Manchester United were confused about how to stop Sigurdsson and Ayew, and ultimately paid the price.

Both goals came from a very similar situation, when Shaw was in an advanced position and Blind was dragged out towards the flank to cover. First, Sigurdsson burst down the right and crossed for Ayew to head home at the far post. Then, Ayew turned provider, breaking down the right and curling a magnificent pass in behind United’s defence for Gomis to finish coolly.

Tactical changes often have a subtle influence on matches, but Monk’s dramatic change in system completely altered the game, and it is unusual to hear both managers with precisely the same view of the game’s dominant moment.

“We did change – we felt they were overloading us in the middle, so we went to a diamond after 10 minutes in that second half,” Monk said. “I explained it to them at half-time – and we ended up getting two quickfire goals.”

“The opponent changed their shape,” Louis van Gaal agreed, when asked why Swansea had mounted such an impressive fightback. “At 1-0 they changed their shape and we couldn’t cope with that.”

It was unusual to see Van Gaal tactically outwitted, and equally unusual to hear him admit it so readily. The Dutchman said his players should have remained more compact, but youngsters like Shaw and Blind need guidance, and it was down to Van Gaal to react to Monk’s switch, perhaps by asking Shaw to be aware of movement in behind him. More crucially, it was further evidence Monk has become one of the Premier League’s most intriguing coaches.