Among plenty of discussion about Arsène Wenger’s decision to abandon the four-man defence he has used for 20 years in favour of a back three it was notable that Mauricio Pochettino’s Tottenham were essentially playing both systems simultaneously in this 2-0 north London derby win. Eric Dier’s ability to play in both defence and midfield meant Spurs seamlessly switched between the systems, nullifying Arsenal’s major attacking threat and putting themselves in control.

Spurs were more 4-2-3-1 than 3-4-3 but, with the full-backs Kieran Trippier and Ben Davies flying forward, Dier dropped back from his defensive midfield role into deeper, right-of-centre positions to stop Arsenal from finding Alexis Sánchez quickly. “I think today you can see our flexibility in our tactics during the game,” said Pochettino afterwards. “How sometimes we had three at the back, four at the back, two at the back with three midfielders, we used the full-backs higher or close inside like a midfielder.” At times Tottenham’s flexibility works so efficiently that their shape transcends numerical formations.

Arsenal’s system at least offered defensive numbers and throughout the first half Wenger’s side were admirably compact, refusing to let Christian Eriksen find space between the lines. They suffered in wider areas, however, and Tottenham built play down their left, behind Mesut Özil, who is neither a keen defender nor particularly comfortable out wide. Tottenham’s two best first-half chances were curiously similar, with Dele Alli and then Eriksen missing from point-blank range at the far post, after deflections fell invitingly. It underlined the first half: Spurs on top in a scrappy game.

Arsenal’s performance was similar to their first-half display against Manchester City at Wembley last weekend, unable to sustain possession in the opposition half, with the wing-backs therefore spending longer in defence than in midfield. Their best two moments before half-time arrived when they took a leaf out of Tottenham’s book and pressed in advanced positions to force turnovers – Hugo Lloris was forced out of goal to palm the ball away from Kieran Gibbs, and Aaron Ramsey attempted a decent low curling shot from just outside the penalty box.

It was surprising that Wenger fielded Olivier Giroud upfront against the Premier League’s most aggressive defensive line – the Frenchman is an excellent centre-forward when playing close to the opposition area but Arsenal have looked more dangerous in this system when a centre-forward runs in behind and turns the opposition. It was a surprise to see Danny Welbeck introduced only after Arsenal were two goals down.

At half-time Pochettino had further demonstrated Spurs’ versatility by switching his attacking midfielders. Heung-min Son moved from the left to the right, Eriksen shifted centrally and Alli started from the left. But those players are allowed the freedom to dovetail, and the breakthrough came after Eriksen’s good work down the right and Alli’s close-range finish. The centre-forward Harry Kane had a relatively quiet game, often battling three centre-backs on his own, but drew a foul from Gabriel and scored the second from the penalty spot, maintaining his excellent record in this fixture.

Eventually Wenger turned to Welbeck, who replaced Granit Xhaka, although he was fielded on the flank rather than upfront. This meant Alex Oxlade-Chamberlain moving to a central midfield role as Wenger reverted to 4-2-3-1, and therefore the natural centre-back Gabriel played at right-back and the natural left-back Nacho Monreal became a centre-back. It felt worryingly disjointed and a comeback rarely looked likely.

The game became stop-start – after no bookings in the first 70 minutes, there were four in the next six minutes – which suited the home side. Indeed Spurs could have extended their lead; Petr Cech was far busier than his opposite number and was Arsenal’s best performer here.

The 2-0 victory confirms Tottenham will finish above Arsenal for the first time since before Wenger took charge but Pochettino is keen to state that Spurs have far loftier ambitions than that. In truth, Arsenal’s ‘St. Totteringham’s Day’ celebrations became pronounced in the years when they weren’t regular title challengers, almost as a consolation for genuine success. There’s a sense that this Tottenham side aren’t looking over their shoulders, but instead looking up the league table towards the summit. Overhauling Chelsea this season will be tough, but Tottenham have already achieved their record Premier League points haul, and are almost guaranteed to finish in second, their highest league placing since the 1960s. It owes much to their hugely impressive coach, and his introduction of a modern, flexible but extremely well-organised tactical system.