The Croatian winger has made just three starts since his deadline day move from CSKA Moscow but he will feature in Thursday's Europa League group stage tie.
Speaking to the club's website, Moyes said of Vlasic: "We really like him. We've been really pleased by him.
"He's come into a relatively settled side which we've got at the moment, but we'll use him tomorrow night and I'm looking forward to seeing what he can do.
"If I had my way, I'd like to let the players have the chance to settle and for everybody to get the chance to know them."
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