After carving out an early lead through Roberto Firmino, the hosts were taken apart twice in quick succession by the Baggies, with striker Jay Rodriguez capitalising on poor defending on both occasions.
And when Matip could only turn Craig Dawson's low cross into his own net before the break, the Reds found themselves facing a deficit they could not overturn in the second period, despite Mohamed Salah's Kop-end strike.
Speaking after the game, the No.32 gave an honest appraisal of his own performance and that of the defensive unit as a whole.
"We started in front, our offensive play was okay, but in the defence we had problems," he told Liverpoolfc.