A frankly ridiculous goal from Daniel Sturridge kept Liverpool's unbeaten start intact on an absorbing, frantic evening at Stamford Bridge that strengthened the title credentials of both sides. Chelsea are the real deal, their component parts gradually slotting into place as Mateo Kovacic and David Luiz increasingly take a starring role.

But the bigger story of the weekend was Manchester United's diabolical performance at the London Stadium where West Ham United won 3-1. The visitors' tactical failures and pathetic attitude suggest Jose Mourinho is just weeks away from the sack.

Here are three things we learnt from the weekend action:

1) Bizarre tactics signal the end for Jose Mourinho at Man Utd

The Manchester United manager so consistently creates drama off the field that it distracts from just how bemusing his tactical decisions have been this season. A general apathy and lack of confidence – manifesting at the London Stadium in a complete lack of pressure on the ball, allowing West Ham to take charge of the game – is the biggest headline, but it is a mistake to think of these traits as purely psychological.

Once again Mourinho, a once master tactician, got his system completely wrong. Firstly, playing three at the back meant confusion throughout: Chris Smalling kept dropping to track Marko Arnautovic while his team-mates held their line; Luke Shaw was wayward in an unfamiliar role and so frequently lost Felipe Anderson; and Scott McTominay was understandably caught out of position for West Ham's third goal.

Using such a narrow formation, with four central midfielders on the pitch, was a ludicrous decision given how compact West Ham had been against Chelsea and Everton, while playing two quick forwards made no sense against a team happy to absorb pressure. It also meant Paul Pogba had nobody to link with, hence his frustration in the middle. Every part of the formation and team selection was wrong, suggesting Mourinho is out of ideas – and hanging onto his job by a thread.

2) Klopp must rotate more to avoid stale attacking patterns

Daniel Sturridge's outstanding equaliser saved Liverpool from a deserved defeat at Stamford Bridge after Chelsea soaked up pressure well in the second half, exposing the visitors' difficulty creating chances in a variety of ways. Mohamed Salah's poor finishing in the first half suggests the problem is not major, but if Liverpool are to win the title they need alternative routes to goal that don't filter so prominently through Sadio Mane and Salah.

These two won't find as much space in the final third this season as opponents drop deep, but of greater concern to Liverpool is an absence of dynamism or creativity in midfield. Chelsea's strength in this area prevented Klopp's side from mustering clear chances in the second half, highlighting a certain predictability that can creep into Liverpool's game.

The solution is to hand more starts to Xherdan Shaqiri (in central midfield) and/or free Naby Keita to play in a more advanced, line-breaking role.

3) Iwobi and Welbeck show the value of fielding players in their natural positions

Unai Emery has been trying to crowbar his best players into his system so far this season and the result has been a slightly disjointed set of performances for Arsenal. Mesut Ozil is not comfortable on the right, often going missing for long periods and failing to adequately cover Hector Bellerin, while Pierre-Emerick Aubameyang's goalscoring has dropped off significantly since he went to the left wing.

Emery's second half substitutions swung the game in Arsenal's favour on Saturday when it looked as though Watford – more aggressive in the tackle and cohesive on the ball – were going to snatch a late winner. Alex Iwobi came on, with Ozil shifted into the middle, and the payoff was huge. The breakthrough came via an Iwobi run down the right, while the second was slotted home by Ozil from his familiar central position.

Iwobi's pace was a huge factor, but more importantly he is simply familiar with the role and its requirements. Emery needs to stop fielding players out of their natural positions if Arsenal are to perform with consistency this season.

Best of the Week – David Luiz

Chelsea's best player on Saturday evening was David Luiz, who not only commanded the defence with some crucial blocks, tackles, and interceptions, but showed his composure in possession to help is side outmanoeuvre the Liverpool gegenpress. Without his incisive forward passes (one of which led directly to Chelsea's goal) and ability to wriggle free of the onrushing forwards Chelsea simply could not have matched Klopp's side.

Luiz made seven clearances, five interceptions, two blocks, and cleared one shot off the line, often covering expertly for the still-clumsy Marcus Alonso to help minimise Salah's impact. But it was in possession that the Brazilian really stood out; it is easy to see why Maurizio Sarri so quickly brought him in from the cold.

Worst of the Week – Cardiff v Burnley

It was quite possible the worst Premier League game in history in terms of technical quality. Burnley and Cardiff City slogged it out in south Wales with a 55% and 62% pass completion rate respectively. Neither side reached 200 successful passes; they attempted 158 long balls between them, the most so far this season in a single match.

And it wasn't just the passing statistics that ensured this typified the defining attributes of Cardiff and Burnley. The home side were far too wasteful, amassing 20 shots but just five on target, while Burnley defied the xG metrics by scoring twice despite attempting a grand total of three shots. There is no right way to play football and certainly no such thing as anti-football… but there's a reason why we laud the high-tempo passing football of promoted sides such as Swansea City or Huddersfield Town in recent years.