It looked like another routine night for the Blaugrana after Luis Suarez opened the scoring with just 10 minutes on the clock, but less than five minutes later Cristiano Ronaldo pegged the Catalan club back.
Despite playing the entire second half with a man less, Barce re-took the lead when Messi himself slammed the ball into the back of the Madrid net prompting wild scenes of celebration.
However, the Portugal forward hurt his ankle in the process and was substituted at halftime.
"How long he will need I can not tell you, but for him it is a small problem", Zidane said. "We will have him ready (to play)". It was mainly Madrid until the final whistle, but Barcelona held on with few problems to continue their unbeaten run and cement their domestic dominance. In a Clasico where there was nothing at stake, it was a great game.
The joy at Camp Nou was short-lived.
Ronaldo appeared to shake off the injury.
Madrid were stamping their authority on the contest, Ronaldo heading over and drilling wide either side of being denied at close range by Marc-Andre ter Stegen. Suarez felt he had been elbowed by Sergio Ramos, prompting the first round of scuffles, before Messi was booked for flying into the defender on the touchline.
And Sergi Roberto then saw red before the break for lashing out needlessly at Marcelo.
On that play, Messi received a pass from Suarez.
- Gareth Bale scored his second goal in El Clasico after the 2014 Copa del Rey final and his first in LaLiga. Real, without a hobbled Ronaldo after the break, equalised again through Gareth Bale and couldn't find a late victor. With most of the players visibly exhausted and struggling to recover on defense, both sides had chances to get the win.
"He told me around a month, a month and a half ago", Valverde said. "That's the positive. We're happy because we can still end the league season without losing".