Ronald Koeman’s disastrous decision to field a three-man defence for the first time since August 20 helped Chelsea to inflict upon Everton one of the most one-sided thrashings of the 2016/17 Premier League season.

Two back-threes

Despite not configuring his side in a 3-4-2-1 formation since Everton’s opening two fixtures against Tottenham and West Bromwich Albion, Koeman was widely expected to match the shape in which Antonio Conte’s side have achieved such recent success.

Although the former Southampton boss did in fact supplement his rearguard with a third centre-back as predicted, that addition was within the confines of an unfamiliar 3-5-2 system, with Yannick Bolasie shifted inside to partner Romelu Lukaku up front.

The rationale under which Koeman made this pre-match change was exceedingly difficult to divine, as the Toffees found themselves outmaneuvered in all areas of the pitch throughout a torrid first-half.

Everton’s midfield woe

In central midfield, Koeman’s three-man barrier consisting of Gareth Barry, flanked by Tom Cleverley and Ross Barkley, was presumably designed to limit the influence of dual number tens Eden Hazard and Pedro. Instead, Hazard underlined the importance of the suspended Idrissa Gueye by frolicking in the pocket of space behind Cleverley, from which he ran to initiate his wonderful opener.

The turn that facilitated the through ball for Pedro’s assist of Marcos Alonso, one minute later, was also executed in that zone, taking both the covering Barry and centre-back Ashley Williams completely out of the game.

Although Bolasie sporadically dropped goal-side of either Nemanja Matic or N’Golo Kanté, Everton’s central cohort were completely overrun by Chelsea’s foursome, thus preventing any service – regular or otherwise – to their isolated strikeforce. The visitors’ first and only effort on Thibaut Courtois’ goal arrived in the 71st minute, when substitute Kevin Mirallas headed wide from a corner-kick.

At any rate, with a spare centre-back at hand at all times, the hosts were unlikely to be troubled by the kind of dual-striker system that a three-man defence is tailor-made to smother.

Chelsea wing-backs ascendant

In wide areas, Koeman’s decision to dump the 4-2-3-1 that triumphed over West Ham United on Sunday deprived his side of wingers to pin back Conte’s rampant wing-backs Victor Moses and Marcos Alonso. Instead it was Everton full-backs Seamus Coleman and Bryan Oviedo who found their upfield forays severely limited by their opposite numbers’ advances, while both were also regularly dragged infield by their side’s midfield shortcomings.

Alonso ran off the back of Coleman to score Chelsea’s second goal, and delivered the back-post cross from which an unmarked Moses hit the post with his 34th-minute strike. Moments after that chance, Moses advanced unchecked again to deliver a pinpoint cross that Diego Costa glanced wide, prompting Koeman to finally introduce Mirallas off the bench to keep tabs on the Nigerian in a 4-1-4-1.

Although more sensibly configured in open play, Everton’s set-piece haplessness ended the game as a contest just before half-time, when Barkley allowed Matic to get ahead of him at the near post, and Lukaku failed to mark Costa at the back.

Second-half

Everton emerged for the start of the second-half in their third unique formation of the evening, with Barkley returned to the number ten role, creating more midfield space for Hazard and Pedro to collaborate on a right-sided overload for the fourth goal.

When Matic robbed Lukaku to spur the fast-break that fueled Pedro’s fifth, repeating the feat the Serb inflicted on an overmanned Barry for the opener, any hope of Everton salvaging their dignity, and limiting the damage wrought by their manager’s unnecessary tinkering, had been long extinguished.