Darren Moore says Albion must take their defeat at Leeds "on the chin" and respond immediately.
The Baggies were beaten by two goals in either half at Elland Road, a result which lifted Leeds to the top of the Sky Bet Championship table.
Moore admitted the performance was below par and called for a quick response to the setback next week.
He said: “It’s obviously really disappointing.
“We gave ourselves a mountain to climb in the game.
“It was an uphill battle after the two first-half goals.
“You don’t ever want to go a goal down early in the game, especially coming up here.
“It’s a result that’s a hurtful result but we have to take it on the chin.
“We’ll have to pick the bones out of it.
“We can only apologise to the fans who travelled for that performance.
“I don’t think any of us saw that coming. We didn’t have a good performance and I need to look back at it and assess where we should have been better.
“We’ll look for a response next week.”