With just one of the Premier League's top four sides collecting all three points, this was a weekend in which the gloss was removed from 2016/17's standout performers.
Pep Guardiola, Mauricio Pochettino, and Jurgen Klopp will all be acutely aware that there is much hard work ahead.
At the other end of the table things have begun to settle into a coherent – and predictable – pattern.
Hull City's back-to-back wins in August are already a distant memory, whilst defeats for Sunderland and Middlesbrough saw them sink further into trouble just as West Ham United begin to climb back up the standings.
Here are three tactical lessons we learnt from the weekend action...
1) Amartey is no Kante replacement; Ranieri might need to abandon his 4-4-2
Claudio Ranieri's 4-4-2 formation was completely inappropriate for this fixture.
Chelsea continued with the 3-4-2-1 trialled at Hull a fortnight ago, using wing-backs to confuse the opposition and two central attacking midfielders.
Eden Hazard and Pedro – who was outstanding on Saturday – both lurked in similar pockets of space behind Diego Costa, and poor Daniel Amartey simply could not cope.
The Ghanian managed a woeful one interception and zero tackles across the 90. He simply did not understand how to cut off Chelsea's passing lines, when to press onto Hazard or Pedro, or how to watch both players simultaneously.
His poor performance was made even more painful by the fact that N'Golo Kante was so effective for their opponents – making three tackles and four interceptions in a typically commanding display.
Without Kante, Ranieri's 4-4-2 formation is beginning to look light on numbers in central midfield, something which opposition managers have clearly picked up on. Antonio Conte's use of a 3-4-2-1 was specifically designed to outnumber Leicester in the middle of the park, as was Jose Mourinho's use of Jesse Lingard and Juan Mata as joint central playmakers in their 4-1 win over Leicester last month.
Ranieri made the problem worse by abandoning the use of a deeper striker in this fixture, but even with Shinji Okazaki in the side they would be too light.
In short, Leicester need to replace Kante with two players, not one. Let's hope Nampalys Mendy can return to action sooner than later to lend Amartey a hand.
2) Emre Can's and Daniel Sturridge's performances show Liverpool lack strength in depth
Jose Mourinho was correct to accuse Liverpool of playing conservatively on Monday night, having identified that Jordan Henderson and Emre Can effectively played the same role in central midfield.
It is unlikely, however, that this was a deliberate strategy from Klopp; as Brendan Rodgers discovered, Can only seems capable of playing in a static role that relies on sideways passing.
Adam Lallana and Georginio Wijnaldum were not adequately replaced in this match, which confirmed that Liverpool do not currently have enough strength in depth.
Can's awkward passing and rather aimless shuttling on the ball completely stunted Liverpool's high tempo build-up play, whilst Daniel Sturridge produced another lacklustre performance up front.
He drifted out wide at the wrong moments and failed to make the bursting shuttle runs required to link his team-mates together.
Neither of these players are suited to Klopp's aggressive counter-pressing system, and yet both will be given a significant amount of playing time – at least until January.
3) Bilic finds the formation that will end West Ham's rut
Slaven Bilic may have got the idea for a 3-4-2-1 formation from watching Chelsea at Hull, because this was an almost identical system.
It worked perfectly, and West Ham were balanced in every area of the pitch.
Cheikhou Kouyate stepped out from the back three to provide support as a third central midfielder, and the use of wing-backs allowed Manual Lanzini and Dimitri Payet to dominate in central attacking midfield.
This match was won in the opening half hour, when the Hammers' dominance of possession led to the opening goal and set the tone for a confident performance.
James McArthur drifted into attack too frequently for Crystal Palace, leaving Lanzini and Payet free to find space on either side of Joe Ledley. Palace had no idea how to track the wing-backs (largely because the lurking threat of Payet drew their formation inwards), which led directly to the winning goal.
Bilic deserves enormous credit form gambling on a new tactical system. Expect a strong run of form to follow.
Player of the week - Joe Allen
Mark Hughes has shifted Joe Allen into a more advanced position this season than the Welsh international is used to, and so far it has been a resounding success.
His double against Sunderland took his tally for the season to four – already his best goalscoring record since 2011/12.
As high pressing becomes the fashion in the Premier League, the pitch has become compressed and playmakers are finding less and less time on the ball.
As a result, nippy little Xavi-types like Allen are suddenly more useful in advanced positions than they used to be, providing creativity by opening up space for their supporting inverted wingers. Hughes should be praised for seeing the benefits of playing Allen in his new role.
Flop of the week – Ahmed Elmohamady
Mike Phelan does not have a big squad to work with, but fielding such an attacking player at right-back was surely a mistake he should not have made.
AFC Bournemouth easily tore through Hull City on Saturday, making a mockery of their good start to the season and confirming that the Tigers are still firm favourites to go down.
Elmohamady had a torrid time against Jordon Ibe, and only managed to make two tackles all match.
In fairness, Robert Snodgrass was equally ineffective on the same flank. Pretty much any Hull player could have been selected for worst player of the week.
By Alex Keble