Juventus coach Massimiliano Allegri believes Marouane Fellaini made the difference and helped Manchester United to a 2-1 win in the Champions League.
Fellaini was introduced with United trailing to Cristiano Ronaldo's stunning volley and the visitors claimed a surprise win thanks to Juan Mata's free-kick and an Alex Sandro own goal on Wednesday.
The Belgium international almost got on the end of Ashley Young's set-piece that led to the winning goal and Allegri said Fellaini was decisive in the Group H clash.
"In the first game, they didn't have Fellaini and we used his absence to our advantage," Allegri told a news conference.
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"Tonight, he played and his physical presence was immediately felt. He controlled some high balls, although sometimes we were good at playing the ball on the ground.
"Conceding those free-kicks was our greatest mistake. That happened and we paid the price.
"We'll have to learn from that."
Juve remain top of Group H on nine points, two clear of United and well ahead of Valencia (five) and Young Boys (one).