Sancho struck in the midweek Champions League win at Villarreal - his first goal for the club.
As a player sometimes it takes a bit of time to adapt," Carrick said. “As a younger player coming to such a big club and a new league it's not easy just to hit the ground running. We were well aware of that.
“Of course we believe in him. The potential he has got is massive. If he can keep doing the right things and keeps himself on the right track he's got a great chance.
“I'm not surprised by what he did the other night. I've seen it in training. I've seen the spring in his step, and in his body language. There's a little spark and hopefully that spark gets bigger."
Tuesday was arguably Sancho's best performance in a United shirt, not just for his goal but also for his work rate going in both directions – something that could be a major factor under incoming coach Ralf Rangnick given his intensive style.
“He's never happier than when he has the ball at his feet and he's trying to create things and go at the defender," Carrick said.
“But the biggest thing the other night was the other side of his game, the attitude and work-rate and mentality. I thought he put in a whole performance the other night.
“He's got a massive future ahead of him if he does the right things with the right attitude."
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