This current international break has been one of the worst for big players of different clubs as the reports of injuries has been numerous. A lot of first team players of the big European clubs has picked up injury in this international break and it's definitely gonna affect the performance of affected clubs.
Gavi has been one of the best players (if not the best player) of Barcelona since the start of the season and surely his injury which the duration hasn't been announced is gonna be a big blow to Xavi Hernandez's teams. His injury adds to the series of Barcelona players that are currently sidelined as a result of injury
True, there have been many players injured. Even some were also facing serious injury that forced them to absent from the league till the end of season. It was cost the club a lot. This is why some players used injury as an excuse to avoid the international break.
Losing one of important players will be greatly affecting the performance from the club. You can imagine if club was losing a guy who has most contribution to the club.
This is a disaster for the club. It's casued by you can't even guarantee that if the second player will able to show the same performance like him.