Moyes is not prepared to offer up any excuses after the 2-1 loss.
"It was a poor result and a poor performance," said the Scot.
"We never really got going. We had a lot of the ball in the first half and never made many chances from it.
"They always looked a threat on the break, in the first half especially and even more so in the second half.
"We missed that spark and West Brom deserved it no question. I can't argue with that."
After putting the misery of last weekend's Manchester derby defeat behind them with an excellent midweek win over Liverpool, this latest setback was completely unexpected.
"We wanted to try to keep that momentum going," said Moyes.
"There were signs but the performance went on to be a poor one.
"I'm concerned after but only because we didn't play well.
"There's a lot of games to go and we can put it right."
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