The England international was selected to start the 1-0 win at Wembley after suffering a dip in form in previous matches.
The 21-year-old managed to break the deadlock against Tottenham's Championship opponents in the 65th minute, and Pochettino was happy with what he witnessed.
"For me, Dele Alli is a top player," Sky Sports News quotes Pochettino as saying. "He is a key player for us. I think he helps us by scoring today.
"I am so happy with him. It's true that everyone can do better but I am happy. It is a period that he needs to find his balance but I am so happy, his performance was good. He tried and scored and that is fantastic."
Tottenham are next in action this Saturday when they face West Ham United at the London Stadium.