Shortly before Pep Guardiola finally took Manchester City to Champions League success two years ago, he reflected on the extra quality that had made his side more fearsome in Europe.

“I learned this season when you play against (Bukayo) Saka, Vinicius (Junior), (Gabriel) Martinelli, (Mohamed) Salah or (Sadio) Mane, you need a proper defender to win duels one-v-one,” he said on Sky Sports. “In the Champions League, at that level, they need one action to beat you and Nathan Ake gave us that boost that I didn’t have in the past. The biggest boost was having a proper defender. In the past, we didn’t have it.”

It would have been difficult to imagine the Guardiola of a decade beforehand talking about the importance of individual duels. But he had been convinced.

On Wednesday, his former side Bayern Munich easily overcame Bayern Leverkusen, defeating Germany’s reigning champions for the first time since Xabi Alonso took charge. When Leverkusen have defeated or outplayed Bayern recently, it has tended to be about shape, space and combinations. But Bayern’s victory was, above all else, about the importance of the duels.

The statistics show Bayern’s superiority in that respect, although if anything, they underplay how physically dominant Bayern were.

Their tackle success rate was 82 per cent compared to Leverkusen’s 54 per cent. Bayern won more duels on the ground, and more in the air. They were quicker to second balls. If the game was hyped beforehand as a meeting between Germany’s two outstanding attacking midfielders, Jamal Musiala and Florian Wirtz, then the difference here was Musiala is more comfortable under close physical pressure from opponents, better at dancing away with the ball at his feet.

At one stage, shortly before the end of the first half, Wirtz attempted a dribble through the middle and ran into his team-mate Amine Adli, leaving both on the ground. That was a — somewhat slapstick — demonstration of Leverkusen’s inability to cope physically.

And Leverkusen weren’t merely the victims of a physical, scrappy game. They were actually the cause of it.

Alonso’s choice of Matej Kovar in goal was something of a surprise, considering Lukas Hradecky has generally been the No 1 this season. But more surprising was the extent to which Leverkusen’s goalkeeper kicked long. His percentage of passes ‘launched’ downfield — defined by Opta as 40 yards or more — was 70 per cent. Leverkusen’s average launch rate this season has been 29 per cent. Only once, in a 2-2 draw at RB Leipzig, had it previously been over 50 per cent. Sure enough, Bayern won 58 per cent of the aerial battles, a figure that was 79 per cent before half-time.

And, ultimately, the game was decided by four Leverkusen mistakes. Not positional mistakes, not being caught in possession, not even being pressed — just situations where Leverkusen came off second-best in duels.

The first goal was the most obvious example. When Michael Olise crossed from the right flank, Nordi Mukiele had no need to be concerned by what was happening in front of him. The only danger was from behind. And while you could understand if Olise’s cross was deep over his head and found Harry Kane at the far post, it was unforgivable that, despite having a three-yard headstart, Mukiele let Kane in front of him to nod home.

The second goal was even worse. Here, Joshua Kimmich’s cross was miscued so badly it was heading straight for Kovar — to the extent this probably can’t even be considered a duel. Nevertheless, Leverkusen managed to lose it, with Kovar dropping the ball straight to the feet of Musiala to bundle it into an open goal.

Mukiele’s evening got worse when he was shown a second yellow card for raking his studs down Kingsley Coman’s heel, a challenge that looks disgraceful from the reverse angle, with the ball in the air and nowhere near Coman’s feet.

Mukiele looks so shocked that you can only assume it was a complete accident — but, again, we have to put this down as a Leverkusen player getting a duel completely wrong.

Alonso tried to secure the right side of his defence with the introduction of Edmond Tapsoba, but after just seconds on the pitch, he hauled down Kane when battling for a set piece.

Again, it’s so basic, but in these situations, one player against the other, Leverkusen were either overwhelmed or resorted to costly fouls.

We often speak about Champions League ties as being more intricate and tactical than league encounters, particularly over two legs.

But something about them somehow always seems to favour the experienced players and the established teams. Just as Real Madrid can’t beat Atletico Madrid domestically but did so in Europe on Tuesday night, Bayern swatted aside Leverkusen with remarkably little difficulty considering their recent domestic clashes.

There’s no reason a European tie should be so fundamentally different. But, as Guardiola said two years ago, in these big Champions League games, winning the duels seems more important than ever.