West Ham's victory over Manchester United earned the Hammers their first three points at home in the league this season and condemned the Red Devils to a record-equalling worst ever start to a top-flight campaign in 29 years.
What makes the result so significant is that under Manuel Pellegrini, the east London outfit had lost their opening four league games, and are now unbeaten in four matches in all competitions, while the result for José Mourinho meant that his side succumbed to a fourth defeat in all competitions and left them three matches without a victory.
Here are four things the encounter between the two sides taught us.
4. United's Defenders (And the Team, Generally) Have No Idea
The Red Devils have kept just one clean sheet in seven Premier League matches (against Burnley). They kept six at the same stage last season, which indicates a clear contrast in form.
Mourinho tried to rectify the issue by reverting midfielder Scott McTominay into a centre-back, to instil a technical presence, playing in a back-three alongside Chris Smalling and Victor Lindelöf, which ultimately didn't work.
Lindelöf was late in closing-down Andriy Yarmolenko and this led to the Swede deflecting the Ukrainian's strike into the back of the net to make it two before half-time.
Smalling and Lindelöf didn't seem to be on the same wave-length and even when the Swedish defender was substituted shortly after half-time, the former looked out of place. This was evident in West Ham's third goal, which saw Marko Arnautović drift into space, latch onto Mark Noble's pass and slot home - capping off a poor defensive showing from United's centre-halves.
3. West Ham Look Solid Defensively
West Ham's two summer signings started together against Manchester United and they demonstrated a powerful and dominant display. Their presence and ability to read the game were terrific against the likes of Romelu Lukaku and Anthony Martial, who found it incredibly difficult to get the better of them.
The positioning of Fabián Balbuena and Issa Diop together were remarkable considering the strength and pace they were coming up against. They made great recovering challenges and blocks and weren't afraid of getting stuck in at the other end either.
Balbuena headed just wide from an early corner by Felipe Anderson before Diop proved to be another nuisance from set-pieces, flicking the ball into the path of Yarmolenko, who eventually fired home via a deflection.
Mourinho was so impressed with Diop, he even congratulated the scout who found the 21-year-old in his post-match interview.
2. Paul Pogba Is the Scapegoat, and It's Not Fair
Paul Pogba has been made the public scapegoat for Manchester United's poor performances after criticising manager Mourinho's tactics, which led to the Portuguese stripping the midfielder of his vice-captaincy.
However, he was unfortunate to be subbed in their encounter against West Ham. In a first-half where Manchester United lacked creativity, Pogba tried to move the ball quickly and get the ball out wide to initiate opportunities, which many failed to materialise.
He was visibly and understandably frustrated on several occasions throughout the match as a result of a lack of movement from his teammates up front, who were well-marshalled by Balbuena and Diop, which led to the former Juventus man resorting to take matter into his own hands and have a pop from-range, which also ultimately came to nothing.
1. Mark Noble Was in the Mood
Mark Noble has settled in well since Manuel Pellegrini utilised the midfielder alongside Declan Rice and Pedro Obiang. The midfielder has looked more combative and assured in the heart of midfield. Picking the right passes, knowing when to press his opponent and when to get stuck in.
He completed 59 passes against Manchester United with an 88% success rate, made three key tackles, unleashed an effort at-goal and grabbed a fine assist for Arnautović with an inch-perfect pass. It was a complete performance from the West Ham skipper, demonstrating his capability in the absence of more creative players such as Jack Wilshere.