Valencia winger Joaquin faces a minimum of three weeks on the sidelines after damaging a muscle in his thigh.
The 28-year-old picked up the injury during his side's 1-0 win over Racing Santander last Sunday.
Joaquin managed to complete 90 minutes at the Estadio el Sardinero but subsequent checks revealed the true extent of the injury.
Unai Emery's side have also been hit by the news that fellow star player David Villa tweaked his hamstring during the clash with Racing.
Valencia will likely have to do without both Villa and Joaquin for their Primera Division meeting with unbeaten table-toppers Barcelona on 17th October.