London - Manchester City's defensive resilience in the absence of the injured Benjamin Mendy faces its first and arguably toughest test when the Premier League leaders travel to champions Chelsea on Saturday.
The 23-year-old France full-back has been in fine form for City since his £50 million pre-season move from Monaco.
But Thursday saw City announce Mendy will undergo surgery in Barcelona on Friday after he ruptured the anterior cruciate ligament in his right knee during last weekend's victory over Crystal Palace.
"Bad news guys - I'll be joining Injury FC on loan for a couple months with ruptured ACL... but will be back soon & stronger hopefully," tweeted Mendy.
City manager Pep Guardiola is under pressure to make good on a huge amount of pre-season spending that saw him splash out more than £130 million on three full-backs alone by bringing major silverware back to the Etihad Stadium.
The Spanish manager, speaking before the full extent of Mendy's injury was confirmed Thursday, said: "We have Danilo, (Fabian) Delph and (Oleks) Zinchenko who can play there so we will see as we go along."
Both City and Chelsea, three points behind both Guardiola's men and second-placed Manchester United, go into Saturday's game on the back of midweek Champions League victories over Shakhtar Donetsk and Atletico Madrid respectively.
But Chelsea manager Antonio Conte is unhappy that, while City played at home on Tuesday, his side have a short turnaround after arriving back in London in the early ours of Thursday morning following their success in the Spanish capital.
"I think we are a bit penalised," said Conte. "Man City is a really strong team. They are scoring a lot of goals (21 in six Premier League games alone), they are in a good moment of form and we have to prepare well (for) this game because it is very important.
"There is the international break (after this weekend)," the Italian added. "My surprise is for this because there is the time (to play the game later)."
United will be huge favourites to beat basement club Crystal Palace at Old Trafford on Saturday.
Far from soaring, the Eagles have lost all six of their league matches so far this season and have still to score their first top-flight goal of a campaign where they have already sacked Frank de Boer and brought in former England boss Roy Hodgson -- a boyhood Palace fan -- in a bid to arrest their slump.
Tottenham Hotspur, fresh from seeing England striker Harry Kane score a hat-trick in a 3-0 Champions League win away to APOEL Nicosia, are at surprise high-flyers Huddersfield while Watford will look to consolidate their position in the top half at West Bromwich Albion.
Elsewhere West Ham, with just Bournemouth and Palace below them in the table, will hope to ease the pressure on manager Slaven Bilic when they welcome Swansea to the London Stadium, while Southampton are away to Stoke.
The pick of Sunday's three Premier League matches sees Newcastle manager Rafael Benitez up against former club Liverpool, who this week drew 1-1 away to Spartak Moscow in the Champions League, at St James' Park in a fixture long known for producing high-scoring encounters.
Arsenal and Everton, fresh from Europa League duty, are at home to Brighton and Burnley respectively.