France international Dembele has been plagued by injuries since arriving from Borussia Dortmund for €105million last August, limited to just four competitive starts for the LaLiga leader.
Speculation has also claimed Barca is worried about the 20 year-old's behaviour away from the pitch but Valverde dismissed those reports after the penalty shoot-out win over rival Espanyol in the Supercopa de Catalunya.
"This question surprises me a bit. All of the players off the field are the most professional in the world to perform on Sunday and in the case of Dembele, they use trusted people, nutritionists," Valverde said. "We are happy with him and he is going to help us a lot."
Dembele was included in the second-string squad for the midweek fixture at Camp d'Esports in Lleida, where Barca triumphed 5-4 in a shoot-out after the contest ended 0-0.
The former Dortmund attacker played 63 minutes against Espanyol.
On Dembele's performance against Espanyol, Valverde said: "Good. He tried to get involved in play and has worked on individuals moves and it is useful for use. Little by little.
"We hope that he translates that into Liga games."