Sunderland paid £7m for the striker who scored only twice in 40 appearances last season, most of the them as a substitute.
Poyet said: "I think last year, unfortunately for all of us, there were too many doubts because of the way we started.
"Now he knows where he's standing, knows he's started later and knows he cannot play 90 minutes right now.
"He knows the importance of maybe the last half-hour for us. That's great for us. He knows his role in the team for the next month."
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