The 32-year-old - who missed Barcelona's opening 1-0 defeat to Athletic Bilbao - is still recovering from a nagging calf injury.
Valverde said on Saturday he wouldn't let Messi play unless he was 100 percent fit. Although he returned to training this week, it was ultimately determined he was some way from a full return.
With Luis Suarez out with a calf issue and Ousmane Dembele sidelined by a hamstring strain, Barcelona are short of options up front. Antoine Griezmann is the only true center-forward available to Valverde.
"He is settling in more and more every day," the manager said.
"What we want is for him to be involved a lot in the game. We know if he is involved, if he is busy and gets on the ball, he can be decisive.
"The other day against Athletic at San Mames, he was not as involved as we would have liked but it is also up to us to help him, to allow our strikers to participate more.
"We have to make our possession more productive, we have to work hard to bring them into play because we know they can be dangerous. It is the same for Antoine."
Carles Perez and 16-year-old Ansu Fati - both members of Barcelona's B team - were called up as cover.