Manchester City closed the gap at the top of the Premier League table to just three points after beating Arsenal 3-1 in a strangely stuttering performance at the Etihad. And while Liverpool dropped points with a nervous display against West Ham United on Monday, Pep Guardiola's side are arguably handling the tension just as badly as their title rivals.
Elsewhere, new strikers in London offered encouraging signs for Chelsea and Crystal Palace fans, while Everton's sloppy defending against Wolverhampton Wanderers raised serious concerns about the long-term future of Marco Silva.
Here are three tactical things we learnt from the weekend action:
1) Guardiola's strange formation betrays the rising pressure on Man City
It should have been easy for Man City to beat Arsenal: stick Leroy Sane on Stephane Lichtsteiner and pierce through the Arsenal midfield with their usual 4-3-3 formation. Instead, Pep Guardiola used Fernandinho in a hybrid centre-back/defensive midfield role that made a 3-2-2-3 with four central midfielders on the pitch. Ultimately it led to the crucial second goal on the stroke of half-time, but it was unnecessarily complicated.
Matteo Guendouzi was excellent for Arsenal, but aside from the young Frenchman they were poor; Unai Emery needlessly experimented with a flat 4-4-2, leaving the Gunners inexplicably light in central midfield when the diamond 4-4-2 could have been ideal to limit City. In Guardiola's defence, his strange system may have been in anticipation of this diamond, with Fernandinho's positional play potentially aimed at tracking Aaron Ramsey from the number ten position.
Whereas Emery's gamble was typical of the Spaniard's constant tinkering in his first season in England, Guardiola's seemed to suggest he is feeling the pressure of a title challenge. It has been eight years since he last won a championship that was fought until the end.
2) Hazard's instinctive partnership with Higuain could save Sarri
Gonzalo Higuain's home debut was far from perfect. He repeatedly misplaced simple passes, and his general link-up play was a little laboured; too often the Argentine slowed things down by turning towards his own goal, or simply gave the ball away with a poor touch. There is a fitness concern that could mean it takes a long time for Higuain to adapt to English football.
However, there was great encouragement in seeing Eden Hazard immediately link well with Higuain. Throughout the match Hazard played first-time passes into the striker's feet, seemingly instinctively understanding how he would move. It was similar to seeing Hazard and Olivier Giroud, with frequent one-twos helping the Belgian to flourish at Stamford Bridge. They exchanged passes 21 times on Saturday.
Higuain's sharp movements were also a cause for optimism. His opening goal suggests Maurizio Sarri's desired high-tempo vertical interchanges will come to fruition now there is a sharp fulcrum ready to make runs in behind.
3) Klopp's lack of a plan B sees Liverpool fall short
What was most striking about Liverpool's nervous performance at the London Stadium on Monday night was their constant attempts to filter the ball through the middle, despite repeatedly failing to create chances using this method. Sadio Mane and Mohamed Salah remained very narrow in a 4-3-3, which made it easy for West Ham to pack the midfield and suffocate the visitors.
Klopp should have made tactical changes to get the ball away from Declan Rice, who made eight tackles, primarily by instructing his forwards to hug the touchline and stretch the play. Liverpool clearly lack creativity in central midfield, which is why Adam Lallana was selected to weave in the right-hand half-space, but Liverpool won't solve this problem unless they change shape.
David Silva and Kevin de Bruyne see so much of the ball in dangerous areas precisely because Leroy Sane and Raheem Sterling start so wide, pulling the opposition's formation apart to create room in the middle. Klopp needs to try this more often.
The tension will only increase in the months ahead, particularly now that a quirk in the fixture list means Man City can go top on Wednesday night and force Liverpool to do the chasing. Greater tactical variety is essential.
Best of the week – Crystal Palace's strikers
Roy Hodgson's Crystal Palace have finally found a striker to relieve the pressure on Wilfried Zaha, finish off their counter-attacking chances, and link with the wide men. It's all they've been lacking for the last 12 months and in Michy Batshuayi Hodgson has the missing piece of the jigsaw. They will easily survive relegation now.
Batshuayi's lovely turn in the penalty area and snap shot led to Palace's second goal, suggesting the Belgian can hit the ground running at Selhurst Park. His arrival also appears to have positively affected Christian Benteke, whose superb overhead kick was probably the best thing he's done on a football pitch in 18 months.
Worst of the week – Everton's defending
Marco Silva teams have always struggled to defend set-pieces, and while that was understandable when managing weaker clubs like Hull City and Watford there is no excuse for Everton's record of 11 set-piece goals conceded this season. The first Wolves goal was dreadfully defended, before further mistakes at the back led to a second and third for Nuno Esperito Santo's team.
Silva's system is often far too attacking, with both full-backs driving forward at every opportunity as Everton look to swarm the opposition into submission. They need to show greater caution in their build-up play to avoid the sort of panicky defensive errors that have allowed Wolves to break five points clear in the race for seventh place.