There’s been plenty of discussion about Albert Einstein in English football this week. One of his most famous proverbs felt particularly apt at the Emirates on Saturday: “The definition of madness is doing the same thing over and over again, but expecting different results.” If this is the case, Chelsea supporters have reason to be concerned about Antonio Conte.

Even in isolation, this was a terrible defensive performance from Chelsea in almost every respect. They were wide open when Arsenal countered, astonishingly deep when Arsenal had possession and incredibly nervous when Arsenal pressed high up the pitch. But what was most concerning, considering Chelsea’s 2-1 defeat at home to Liverpool last Friday, was when their performance without possession was similarly meek.

More than anything, Chelsea’s overall defensive shape was terrible last weekend. Conte set his stall out against Liverpool with a very deep block, his back four dropping back to the edge of their box and the midfield trio retreating into a position just in front of them, completely conceding the midfield ground. They were punished by Jordan Henderson, who took advantage of his time on the ball to produce an unusually assured performance in the deep midfield role, and thumped in a truly astonishing long-range strike.

Surely, then, Conte would have learned lessons from that defeat and used a more aggressive defensive block against Arsenal? No one was asking for Chelsea to play a high line against Arsene Wenger’s pacy attacking quartet, but engaging with the opposition midfield was a must.

Instead, Chelsea replicated last week’s display. Between defence and midfield they were compact to a staggering extent, presumably in an attempt to deny Mesut Ozil space between the lines. But Santi Cazorla and Francis Coquelin were allowed all the time in the world in possession, with the former unsurprisingly capable of dictating the play and knocking quick passes into the final third. Arsenal started on top.

Chelsea’s first concession, however, wasn’t about defensive shape, but rather an individual defensive error. Gary Cahill’s mistake in possession allowed Alexis Sanchez to steal in, run through on goal and calmly dink the ball over Thibaut Courtois. 1-0.

The second goal was a slicker passing move that will have delighted Wenger, but Conte will ask serious questions of his left-winger Eden Hazard, who completely failed to track Arsenal’s speedy right-back Hector Bellerin, typically motoring forward to provide a simple square pass for Theo Walcott to tap in. 2-0.

This is not Hazard’s first mistake in this sense — it’s been a common theme of his period at Chelsea. For all of his brilliant attacking qualities, his mesmeric ball control and searing acceleration, he’s staggeringly sloppy in a defensive sense. As long ago as 2013-14 it cost Chelsea in the Champions League semifinal, when Hazard twice switched off to allow Atletico Madrid defender Juanfran (who, coincidentally, holds Spain’s right-back slot ahead of Bellerin) past him on the overlap for two goals.

It’s reached the stage where Conte needs to consider creating a defensive shape to accommodate Hazard’s sloppiness. Rather than defending with a back four and a line of five, perhaps Chelsea should simply defend with two banks of four, with Nemanja Matic shifting across to cover the left side of midfield. If Diego Costa dropped deeper, as he did so effectively during his Atletico Madrid days, Chelsea could create a 4-4-2 shape without the ball and 4-3-3 in possession. Carlo Ancelotti did something similar with Real Madrid because of Cristiano Ronaldo’s similarly poor defensive qualities.

The shape wasn’t helped, meanwhile, by the use of Cesc Fabregas in midfield. He played his way into the side with two goals in midweek at Leicester City, but here demonstrated precisely why Conte doesn’t trust him in this system. Fabregas played too high up the pitch, creating a gap in Chelsea’s defensive block that Arsenal were able to exploit. Playing both Hazard and Fabregas together in a side seeking to defend so deep was always going to cause problems.

Then came Arsenal’s third goal, which featured Ozil spinning N’Golo Kante majestically, before playing a pass into the path of Sanchez, motoring into the box for the return ball and crashing a bouncing shot in off the far post. 3-0. This time, it was Chelsea’s lack of defensive pace that was exposed, and Conte will be particularly disappointed at how easily Kante was beaten. The Frenchman’s role in this side is to stay solidly in front of the defence, protecting the centre-backs from precisely that sort of counterattack.

Elsewhere, there were other causes for concern in the defence. Ivanovic had another poor game, and his booking for tripping Alex Iwobi — precisely the type of speedy winger he struggles against — felt inevitable. Left-back Cesar Azpilicueta was sucked into narrow positions by Walcott’s running, which emphasised Hazard’s poor work rate, while Cahill again looked nervous in possession midway through the second half, screaming at Courtois for his refusal to sweep from his line.

The Belgian goalkeeper, meanwhile, didn’t make any major errors but his level of performance has clearly dipped over the past 18 months. Unhappy in London and keen for a return to Spain, his questionable commitment has sadly harmed his ability. David Luiz, often considered a poor defender, was arguably the least culpable of the back line.

Conte switched to a 3-4-3 system for the final half hour, which appeared more of an experimental formation in preparation for upcoming tests rather than a genuine attempt to get back into this game. It suits Marcos Alonso, who appeared as a substitute in place of Fabregas (bringing inevitable ironic cheers from the home supporters) as a speedy attacking left wing-back, while Azpilicueta was allowed to switch to the right-sided position he prefers.

Chelsea are hardly in crisis — they’re just three points behind Arsenal and Liverpool — but it’s hugely surprising to see Conte presiding over such a wretched back line. It felt like this was a good game for John Terry to miss against Arsenal’s extremely quick attack, but his organisational skills were badly needed, and if Conte wants to ask his players to defend so deep, there are no better centre-backs in the country than Chelsea’s captain.