Spain midfielder Gavi suffered a serious knee injury in the Euro 2024 qualifying win over Georgia.
The Barcelona player, 19, hurt himself while controlling the ball in space and left the Valladolid pitch in tears.
Gavi is a key player for club and country, with 27 caps for Spain and 111 appearances for Barca.
La Roja, who had already sealed their place at next summer's Euros, won the match and ensured they finish top of Group A above Scotland.
Real Sociedad defender Robin le Normand put them ahead after just four minutes before Napoli winger Khvicha Kvaratskhelia levelled for the visitors.
In the second half, Ferran Torres scored to put the hosts back ahead, before a Luka Lochoshvili own goal sealed the win.
Torres, who also plays for Barcelona, held up team-mate Gavi's shirt to celebrate his goal.
