If pre-season predictions are accurate, then neither Manchester City nor Liverpool can afford any slip-ups during the course of this Premier League season. They are out in front as leading contenders and, if this campaign follows the pattern of the previous one, the fate of the trophy will again by defined by the smallest margins.
On paper it was the champions and treble winners City who had the more difficult start with a trip to the London Stadium to countenance. But Pep Guardiola's team shook off some first-half cobwebs to ease to victory and match the three points gained by Liverpool against Norwich on Friday night.
City were rhythmic and for the most part fluent with the patterns Guardiola seeks in his attacks already instilled at this early stage. A Raheem Sterling hat-trick and a goal each from striking rivals Gabriel Jesus and Sergio Aguero damaging West Ham's pre-season optimism and sending out a devastating message to City's fellow title challengers.
The only new face was Rodri, signed from Atletico Madrid in the summer. He slotted into the system in place of Fernandinho at the base of midfield and, when he has time and space, gets City going beautifully.
Rodri will however have to be wary inside his own half when it comes to being put under pressure. One incident early on saw him shaken down for possession by Manuel Lanzini and fortunate that the VAR check produced no penalty when an attempt to win the ball back was examined.
Other than that, however, he was used as the out-ball whenever City tried to get through the first line of the West Ham press. They didn't mind going back to Ederson if needed and it was the Brazilian goalkeeper's clever clearance to Oleksandr Zinchenko that set them on the move towards their first goal.
The signing of Joao Cancelo might well have Kyle Walker sweating for his position at right back but the England defender was excellent here and his powerful overlapping run culminated in a perfect cross for new No.9 Jesus to tap home at the front post.
Where title rivals Liverpool have been content to bypass additions in the transfer market, it has been Guardiola's willingness to put pressure on his own player with new arrivals that marks this City side out as ultra-competitive and ultra-focused.
Many Fantasy Premier League players were left vexed by Guardiola's decision to bench both Aguero and Bernardo Silva - arguably their two best players of an historic title-winning campaign last season - but City didn't miss a beat without them.
Jesus has looked sharp in his minutes since winning the Copa America with Brazil, with Aguero left kicking his heels and waiting for a chance to get back in.
Another summer international title winner in Riyad Mahrez was given the starting shirt up front with Leroy Sane now ruled out as a long-term absentee. But this is not a team composed of 11 players, there are now 15 or 16 players capable of coming in and playing to Guardiola's exact specifications.
As well as Bernardo and Aguero, the bench also contained Ilkay Gundogan and Cancelo. Such depth simply doesn't exist at other clubs.
And Mahrez played his part in the second goal, winning a midfield ball and setting Kevin De Bruyne on the course towards providing Sterling with a relatively straightforward finish. The England forward wants to take his goalscoring to the next level this season and that has got him off to a strong start.
It should have been three moments later as City turned the screw at the start of the second half. However, they were to be denied by the VAR. Sterling's cut-back to Jesus for a tap-in was deemed by referee Mike Dean to have been made from an offside position.
If these are the standards by which the VAR will be measuring incidents this season - its first application in the Premier League - then it's fair to say things are going to get contentious. One camera angle placed Sterling's chest the wrong side of Ryan Fredericks by a matter of centimetres but that was enough to see the goal chalked off.
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It was a shame, too, as the move preceding it provided an example of the kind of football Guardiola wants his men to play. David Silva's flick into Sterling was exquisite and well-measured, characteristic of one of the Premier League's greatest-ever players who must be cherished in his final season.
It was all rendered academic with 15 minutes to go when Sterling got his second and the long-awaited third for City. Mahrez breached the West Ham back-line with his lofted through ball and Sterling's expertly-timed run brought a looping finish over Lukasz Fabianski.
VAR was to have its moment again before time was up with the West Ham goalkeeper judged to have moved before Aguero's spot-kick was blocked. It was a poor penalty but the Argentine got a chance to make amends while the West Ham fans chanted "What the f*ck is going on?". It will take some time to get used to.
Sterling struck again at the near post near the end off another Mahrez assist. City's habits in the timing of their runs and through balls was too good for West Ham on the day - and too good for VAR as well.
City now have plenty of time integrate their few summer signings and get their summer internationals back to full steam with only one match a week in the early part of the season. Next up will be Tottenham, who knocked them out of the Champions League and - arguably - denied them the clean sweep.
Pep, City and Sterling look formidable at this point with little to no summer hangover. Your move, Liverpool.