The 0-0 Champions League draw was Messi's first appearance of the season.
Valverde said afterwards: "He is the same way any player would be who didn't do a preseason and had only done four or five sessions with the group.
"With hardly any preparation, he had came into a game that was already underway. It's the first game with him and also the first full game for Luis Suarez. It's the first step because we need the players in attack who play together."