Dembele – who has attracted attention in recent weeks for a reported bad attitude – was one of the few bright sparks, bamboozling Villarreal's defenders with an array of tricks and flicks.
He also delivered a telling contribution for his side's opener after 36 minutes, Gerard Pique heading home the Frenchman's cross from the right.
Carles Alena scored his first La Liga goal for the club late on to seal the win, but it was the contribution of Dembele that Valverde wanted to highlight after the game.
"He was one of the most prominent players in the game," he told a media conference.
"He did so many good things and we expect many good matches to come.
"What stands out was his speed, dribbling, shooting and change of pace."
Barca toiled for long periods against their lowly opponents and Valverde believes his side needs to learn to play better when they are not in possession.
"In the second half we lacked possession of the ball and we suffered," he added.
"They became strong and we had to organise ourselves, so they would not become more dangerous.
"We are not satisfied with what we have seen when we don't have the ball."