Sporting Gijon hold a slender lead over Osasuna after 90 minutes of Copa del Rey fourth-round action at Estadio El Molinon.
Gaston Sangoy scored the game's only goal on 14 minutes.
The 28-year-old Uruguayan forward has now found the net twice in his last four appearances.
The two sides will meet for the return leg at El Sadar Stadium on November 28.