Liverpool lost for the first time all season as West Ham won a thrilling game at the London Stadium.
The Hammers took the lead in fairly bizarre fashion just four minutes in when Pablo Fornals' corner was knocked into his own net by Alisson, who had complained that he was fouled.
Liverpool levelled four minutes before half-time with a fine free-kick from Trent Alexander-Arnold, but the Hammers almost retook the lead at the start of the second period when Declan Rice headed against the bar.
Sadio Mane and Mohamed Salah both missed good chances to put Liverpool ahead, and they were made to pay when Fornals raced clear on the break to make it 2-1.
An unmarked Kurt Zouma soon made it three with a header from a corner, and despite substitute Divock Origi pulling one back, Liverpool's club-record equalling 25-match unbeaten run came to an end.
West Ham were terrific and showed teams exactly how they should play against Liverpool, with David Moyes' plan coming off perfectly.
The hosts benefitted from the slightly fortunate opening goal of course, but after that they strung their defenders across the width of the penalty box and turned the game into one without width.
Liverpool struggled in that environment, with Salah having one of his least effective games of the season in front of goal.
Alisson was credited with the own goal that put West Ham ahead
The visitors' uncertainty in midfield was exposed as well, and that is an area which must now concern Jurgen Klopp.
If Alisson looked a little shocked that the early goal which ultimately went down against his name was allowed then that's because he had every right to be.
The modern goalkeeper is very strong and athletic, but also usually very protected in situations such as being surrounded by the arms and leaps of Michail Antonio and Angelo Ogbonna.
The goalkeeper probably wasn't directly fouled, but he was certainly knocked off balance by the attention of the Hammers duo and that, usually, is enough to penalise the attacking side.
It was a 50-50 decision, but the element of surprise around the ground when that decision went West Ham's way was palpable.
There were a few stray balls as he looked to force the issue, but that's just part and parcel when you're a player who looks to make things happen. We all know that this is no average right-back.
That was again underlined with the brilliant free-kick he struck to level the scores just four minutes before half-time, when he could hardly have placed it in a better spot.
It is perhaps no surprise given that he has largely had a life of playing in multiple positions, but Antonio plays the centre-forward role as though he were two players.
Simultaneously the battering ram and the pacy threat in behind, the West Ham forward is a nightmare for even the very best of centre-backs, of which Liverpool have two.
