Diego Costa sends Chelsea to the top of the league

Middlesbrough 0 Chelsea 1

Goodness knows how high on the scale Antonio Conte’s blood pressure might have registered had he nipped out at half-time and visited the NHS “health bus” in the car park offering fans mini check-ups.

Watching the Chelsea manager’s technical-area hysterics in isolation it would have been easy to imagine his side were locked in a desperate relegation struggle rather than en route to the top of the Premier League courtesy of a sixth straight victory.

Considering they have not conceded a single goal during that sequence Conte generally has cause for serenity but, on this occasion at least, his extreme agitation was at least partially justified by a determined, sporadically dangerous Middlesbrough performance.

By the end Diego Costa’s volley had reignited Boro’s relegation worries but Adama Traoré’s pace and the midfield steel of Aitor Karanka’s two Adams, Clayton and Forshaw, left Chelsea looking slightly relieved.

Karanka’s switch from his beloved, if sometimes rather rigid, 4-2-3-1 formation to a much more flexible version of 4-3-3 helped the recent mini renaissance featuring draws at Arsenal and Manchester City.

Here that configuration saw Gaston Ramírez in a left-sided role presumably intended to stretch Victor Moses, the right wing-back in Conte's 3-4-3 system, and Ramírez started well, posing Chelsea – and Moses in particular – quite a few early problems.

The Uruguayan was involved in the buildup to an early chance which saw Alvaro Negredo – seeking his first goal since the season's opening day – slicing over from six yards. It proved the cue for a disappointing, less than mobile, afternoon for the forward which must have made the benched Jordan Rhodes wonder what he has to do to be offered a start by Karanka.

At least Ramírez was showing some ambition. Later some woeful decision making would let him down but if he initially, briefly, looked capable of eclipsing even Eden Hazard it hardly helped the latter's cause that he appeared to be singled out for some rough stuff by Karanka's midfield.

After seeing Hazard clattered by a trio of early challenges, most notably from Marten De Roon and Clayton, Jon Moss, the referee, finally booked Clayton for a particularly nasty late lunge at the Belgian's ankle.

If Hazard’s targeting probably did not come entirely as a surprise, Conte looked a little bit frustrated by Boro’s surprisingly effective amalgam of caution and aggression. Superbly compact as Chelsea advanced, with Clayton and Forshaw especially impressive, Karanka’s players were not frightened to counterattack, utilising Ramírez’s skill and Traoré’s blistering pace to, at times, perturb the visiting back three.

It all dictated that, until Costa’s goal, Victor Valdés had a rather quiet first half. Admittedly the former Barcelona and Manchester United goalkeeper made one outstanding save when he diverted Pedro’s goalbound shot for a corner following exemplary approach work on the part of Hazard and Moses, but, generally, he was hardly overworked.

Valdés did though enjoy one rather fortunate reprieve when he miscued a clearance and watched horrified as it to fell to Marcos Alonso. An empty net beckoned but, somehow, the left wing-back directed the ball towards a corner flag instead.

As half-time approached Costa had been largely anonymous with Ben Gibson and Calum Chambers keeping him uncommonly quiet but then, in the 41st minute, a chance finally fell the centre-forward’s way and, typically, he was in the right place at the right time to seize it.

Hazard sent a corner looping high into the air and no Boro player reacted as they should. Valdés, who had just received lengthy treatment for an injury, should arguably have come for the ball as it looped up, while Gibson and De Roon were among those who seemed to lose concentration and temporarily froze. It left Costa free to meet a deflection, extend his left foot and direct a volley into the bottom corner from around six yards. It was his 10th goal of the season.

The second half began in similar vein with Moses and Hazard creating an opening for Alonso repelled by Valdés with Chambers then doing well to block Pedro’s attempt to pounce on the rebound.

By now Moses was increasingly influential as he delighted in reminding everyone that Fabio da Silva was deputising for the injured George Friend at left-back and it was his first appearance of the season. Sensibly Karanka replaced Da Silva with Stewart Downing, who possibly should have started at full-back, after an hour.

As icy rain poured down Ramírez shot over the bar from an inviting position after Clayton had begun reasserting himself against N’Golo Kanté and co and De Roon had won the ball in Kanté-esque manner.

Chelsea's minds seemed to be wandering and it took some touchline gyrations from Conte – cutting an infinitely livelier figure than Negredo – until they refocused and Pedro's shot hit the bar following fine work from David Luiz and Costa.

Even so they had Thibaut Courtois’s first significant, simply superb save for denying the suddenly energised Negredo after Traoré’s pace had once again caught Chelsea cold.

Unfortunately for Boro, it was too little, too late.

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