Demebele, who joined Barça in summer for a fee of €105m rising to €145m, appeared from the bench for the final half hour of Thursday night's 5-0 Copa del Rey rout of Celta Vigo.
The French winger even contributed an assist as the Catalans cruised through to the next round after winning 6-1 on aggregate, but was later seen in discomfort as he left the pitch holding the same area as the final whistle sounded at Camp Nou.
Speaking to the media afterwards, Valverde described the discomfort as 'nothing special'.
But he also praised Dembele's performance, stating in quotes published by Mundo Deportivo, "I have seen Dembele very well. He is a player who, as soon as he takes the ball, knows that something will happen. He has something different to the rest."
"The first half was extraordinary on every level," Valverde said of the game in general.
Following on from the €160m capture of Philippe Coutinho, Colombian defender Yerry Mina also joined Barça this week, competing an €11.8m switch from Palmeiras in Brazil.
Speaking about what Mina can bring, Valverde said, "He is a young player with potential and we thought he could help us out. We'll have to see how he adapts to the league and to Europe."