Arsenal squandered an opportunity to narrow the gap on Premier League leaders Liverpool, suffering a 0-1 home defeat to West Ham.
Jarrod Bowen scored the decisive goal late in the first half, heading in an Aaron Wan-Bissaka cross after starting the move himself.
Despite dominating possession in the second half, Arsenal struggled to break down a resolute Hammers defense.
Their task became even harder when Myles Lewis-Skelly was sent off following a VAR review for a last-man foul on Mohammed Kudus.
West Ham comfortably held on, ending their four-match winless run and moving level on points with Manchester United, while Arsenal remain eight points behind Liverpool.
