Haller has three goals in the Premier League this season, and only 10 since arriving at the club at the start of last season.
Moyes is happy with how the Hammers have begun this campaign, but knows they must get the best out of Haller to step up to another level.
"It's not just the great goals I want him to score," said Moyes to reporters after their draw with Crystal Palace, in which Haller scored.
"We need him to be a big part. We are missing Michail Antonio at the moment and we needed someone to come up with the goods.
"It looked for long periods tonight that we were huffing and puffing and not really getting anywhere but we got a wonder goal from him."
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