With a four-goal lead, Chelsea relented and West Ham created chances for a consolation, but Wilson nodded wide, Sánchez acrobatically tipped Potts’ shot over the crossbar and both Kilman and Aguerd headed over.
Kilman’s block prevented Estêvão netting a Chelsea sixth, but Potter and his players will need to dig deep to turn things around, starting with a Carabao Cup second-round tie at Wolverhampton Wanderers on Tuesday evening.
West Ham United: Hermansen, Wan-Bissaka, Todibo (Potts HT), Kilman, Aguerd, Diouf, Ward-Prowse, Souček (Walker-Peters 69), Paquetá, Bowen ©, Füllkrug (Wilson HT)
Subs not used: Areola (GK), Scarles, Mavropanos, Rodríguez, Irving, Marshall
Goal: Paquetá 6
Chelsea: Sánchez, Gusto (James 69), Tosin, Chalobah (Fofana 69), Cucurella (Hato 69), Caicedo, Fernández ©, Neto, Estêvão (Gittens 77), Pedro, Delap (Santos 61)
Subs: Jörgensen (GK), Gaga (GK), Acheampong, Essugo
Goals: Pedro 15, Neto 23, Fernández 34, Caicedo 54, Chalobah 58
Booked: Hato
Referee: Michael Oliver
Attendance: 62,462