Andrea Pirlo says Weston McKennie needs to improve if he is to become a star at Juventus.
The midfielder joined the Serie A side in August from Schalke on an initial loan that will become permanent at the end of the season.
McKennie, 22, has started 14 of the 22 appearances he has made for the Italian champions, scoring four goals and registering two assists.
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Juve coach Pirlo is happy to have the United States international as part of his squad but is aware that he is still developing.