Valencia will banish a fan who hit Barcelona forward Lionel Messi on the head with a plastic bottle on Sunday for life once they have been identified, the club said.
Messi was celebrating Barca's 94th-minute winner with teammates near the corner flag when someone threw the bottle from the stands and it struck him on the head.
The Argentina captain was examined by a member of Barca's medical staff and did not appear to be hurt, giving the thumbs- up as he walked off the pitch after the final whistle.
"Valencia CF regret and condemn the isolated incident in the game against FC Barcelona, in which a small, uncapped bottle of water was thrown from the stands at opposition player Lionel Messi," Valencia said on their website.
"The club will endeavour to locate the person who threw the bottle and they will be banned for life from the Mestalla," they added.
"Valencia CF operate a zero tolerance policy on such actions and rigorously enforce all security measures set out by legislation."
Barca's 1-0 win kept them hard on the heels of leaders Real Madrid, who are two points clear of their arch-rivals after 13 matches thanks to Saturday's 2-1 victory at Malaga.