What was Kepa thinking?! Winners and losers as Chelsea goalkeeper gifts Manchester City vital victory

Chelsea might have to put in planning permission for an extension to their treatment room, such is the ludicrous amount of injuries they are dealing with right now.

Going into the City game, they already had the likes of N'Golo Kante, Wesley Fofana and Ben Chilwell out of action.

Mason Mount – a player who really doesn't get injured that often – then had to pull out of the contest after "receiving a kick in training" and the midfielder's withdrawal would foreshadow a nightmare 22 minutes where Chelsea were forced into substituting both Raheem Sterling and Christian Pulisic.

This brings their total absentees up to an eye-watering 10 and these selection woes could not have come at a worse time either.

With the Premier League table starting to take shape and their European qualification rivals hitting form, the under-fire Potter needs to have his best players available if his team is to have any hope of closing the gap.

This result was a double whammy for Mikel Arteta's men. Obviously, City have capitalised on their draw against Newcastle and closed the gap on the leaders to five points. But that's not the only reason for Arsenal to be concerned.

With Sterling and Pulisic both injured, Chelsea could be forced into stepping up their interest in the Gunners' primary January transfer target Mykhailo Mudryk.

Arsenal were recently issued an ultimatum by Mudryk's current employers, Shakhtar Donetsk. The Ukrainians want £88 million ($105m) for the winger – a price Edu & Co. are reluctant to pay.

Chelsea are obviously not shy about splashing the cash and with their need for a productive forward having now increased, this transfer saga could be about to get very interesting.

It may not feel like it due to the World Cup, but we are not even at the halfway point in the Premier League season. And, in this injury-filled congest-a-thon, whoever has the deepest squad is going to take some stopping.

That's good news for City, who named an embarrassment of riches on their bench on Thursday.

The most expensive British footballer of all time, Jack Grealish, World Cup winner Julian Alvarez and 2016 PFA Player of the Year Riyad Mahrez were among those taking a pew, with Kalvin Phillips, Manuel Akanji and young guns Rico Lewis and Cole Palmer also available to reinforce Guardiola's starting line-up.

Compare that with the rabble sat a few yards to their left. With all due respect, Bashir Humphreys, Omari Hutchinson and Lewis Hall don't quite carry the same fear factor, do they?

MIdway through the first half, Walker and Cancelo were involved in an abortive piece of link-up play down the right-hand side. As a result of the turnover, Chelsea maneuvered their way into the box, with the excellent John Stones having to explode into action to deny Pulisic a free sight at goal.

Guardiola found the imperfect interchange too much to bear, sinking to the turf melodramatically at the sight of two of his most reliable cogs malfunctioning. He seemed to stew on the incident for the rest of the first half, subbing both Walker and Cancelo at half-time. It was little more than the pair's first-half displays deserved.

Cancelo has been conspicuous in his absence since the World Cup, and this was Walker's first Premier League game since October due to injury.

Guardiola has previously explained that they had been omitted for fitness reasons and, before the game, he even seemed to suggest that their inclusion was the result of fan pressure.

That is probably a lie, but City's improvement after Lewis and Akanji replaced Walker and Cancelo at half-time does not bode well for the latter pair's short-term prospects.

Unless you are Maurizio Sarri, it is hard not to feel at least some sympathy for Kepa. The error that allowed City to edge in front was so out of step with rationality that the entire stadium uttered a collective 'huh', until the replay shed some light on proceedings.

Only the Spaniard will be able to explain exactly what he was thinking letting Jack Grealish's cross trickle through uncontested to Riyad Mahrez at the back post.

However, we can have a pretty good guess at what happened. We believe the scientific term is 'brain-fart'. There is no other possible reason for the heinous mistake. Just when he seemed to be shedding the label of 'error-prone goalkeeper', too.

Grealish and Mahrez treated the early arrivers at Stamford Bridge to a show in the pre-match warm-up, spraying 40-yard, lobbed passes to each other. The ball didn't touch the ground once.

Around about an hour and a half later, the pair were wheeling off to celebrate, having combined to score City's much-needed breakthrough just three minutes and 45 seconds after both being introduced as substitutes.

Grealish was the architect, pulling free of Cesar Azpilicueta before delivering a low cross to the back post, where Mahrez was waiting.

Yes, Kepa might claim the assist, but it was still the perfect outcome for Guardiola, who even treated himself to a rare, satisfied smile when the ball hit the back of the net.