The Hammers slipped to a fourth defeat in six matches since Potter replaced Julen Lopetegui last month as Brentford ran out 1-0 winners at the London Stadium.
Yoane Wissa then had two goals disallowed and Schade hit a post, with West Ham looking utterly powerless to stop them.
Kevin Schade fired Brentford ahead after only four minutes, stabbing home the rebound after his first effort was cleared off the line.
“The first half was nowhere near where we want to be,” said Potter.
“In fairness, credit to Brentford, when we conceded the goal that we did, it almost plays into the game that they want it to be.
