Lionel Messi scored on his club-record 506th La Liga appearance but Barcelona could only bounce back from their Champions League defeat by Paris St-Germain with a draw against Cadiz.
Messi's first-half penalty after Pedri was felled was cancelled out by Alex Fernandez's last-minute penalty.
Cadiz's equalizer, from their only shot on goal, ended Barca's seven-match-winning run in La Liga.
Barca can now be overtaken in third if Sevilla beat Osasuna on Monday.
Barcelona could have moved to within six points of leaders Atletico Madrid if they had overcome Cadiz, who brought their four-game losing run to an end with their late dramatics at the Nou Camp.
Apart from Ruben Sobrino bundling an awkward shot wide just minutes after Messi gave Barca the lead, Cadiz rarely threatened.
But the hosts were left frustrated as Messi's penalty - coolly taken after Pedri was sandwiched in a tackle between Salvi and Isaac Carcelen - was all they had to show despite controlling 81% possession and having 20 shots.
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