The Hammers made the winger's loan deal into a permanent transfer from Brentford yesterday.
Moyes said, "Our plan was to make it permanent in the summer, but a mild medical problem meant we had to hold it back and wait until the time was right.
"Obviously we had any time to do it, and it was always going to get done. That was never in doubt, we just had to make sure the small medical issue was cleared up and we could move on from there.
"I've always liked his goals and assists - he's given us a couple of assists and we're waiting for the goals, but what we've found at the moment is that he's becoming a really hard working team player for us, which we really like.
"Because he's young to the Premier League, there's a lot more development and a lot more to come from him. We always said we didn't want to rush him, and we don't want to - there'll be games when we need to be patient with him and hopefully we end up turning Said into a top Premier League player."
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