Fellaini made a winning debut against Crystal Palace yesterday.
"Marouane is proven in the Premier League so he doesn't need any bedding-in time when it comes to learning the English game," Giggs told United Uncovered.
"That's a big positive. He brings us strength, height at set-pieces and goals from midfield.
"He was really keen to join us and that's always a great quality: when a player is desperate to play for United they're usually determined to make the most of it when they're given that chance. I have no doubt he'll enjoy himself here, playing in the Champions League, playing in the big games."
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