The 21-year-old, who was part of the Spain squad that won the European Championship in July and collected a gold medal with the Under-23s at the Paris 2024 Olympics, had suffered a left hamstring injury earlier in September.
He is expected to be out for around three weeks, Barcelona said. Lopez has scored 11 goals and provided one assist in 45 appearances for the Catalans.
The LaLiga leaders are without new signing Dani Olmo, who is sidelined for up to five weeks with a right hamstring injury, and fellow midfielders Gavi, Frenkie de Jong and Marc Bernal, as well as defenders Ronald Araujo and Andreas Christensen.
Under new manager Hansi Flick, Barcelona have made a perfect start to the season, with five wins from five games putting them top of the LaLiga standings, four points ahead of defending champions Real Madrid.
Barca travel to French club Monaco for their Champions League opener on Thursday.
