Lionel Messi scored an injury-time penalty as Barcelona came from behind to beat Valencia and go top of La Liga.
Messi had given Barca a controversial lead after offside Luis Suarez jumped out the way of his low shot.
Valencia then fought back to take a 2-1 advantage with fine goals from Barca loanee Munir el Haddadi and Rodrigo.
But Suarez equalised for the visitors when he arrived at the back post, before winning a penalty in added time which Messi confidently converted.
The result takes Barcelona a point ahead of second-placed Atletico Madrid, who face Sevilla on Sunday.
Messi holds his nerve against penalty king Alves
Valencia goalkeeper Diego Alves has developed a reputation as an expert at keeping out penalties, having saved 17 of his past 35 spot-kicks before this game.
So when Uruguay striker Suarez was brought down inside the penalty area by Aymen Abdennour deep into injury time the pressure was on Messi.
But he kept his nerve in front of goal and took his tally to 19 goals in 21 games against Valencia - having only found the net more often against Atletico Madrid (21) and Sevilla (20).
The Argentina international's strike also meant Alves has conceded 18 Messi goals, more than any other goalkeeper in La Liga.
Barcelona were, however, dealt a blow when Andres Iniesta fell awkwardly under a strong challenge from Valencia's Enzo Perez.
The 32-year-old midfielder clutched his knee and immediately indicated to the bench he needed to be substituted.
He left the pitch in tears on a stretcher while Barca boss Luis Enrqiue vented his anger at the officials as Perez escaped punishment.
Barcelona said in a statement that Iniesta suffered a "lateral collateral ligament injury in his right knee" and will have further tests to determine the extent of the damage.
With defenders Gerard Pique and Jordi Alba ruled out until next month with ankle and hamstring injuries respectively it places a further strain on Barca's squad.