However, Zidane is hopeful it is not serious.
With the scores level and the LaLiga champions down to 10 men due to Sergi Roberto's red card, Messi bent a brilliant low finish home to put Barca in front.
The result left Real Madrid three points behind city rivals Atletico in the race for second, with a game in hand. There was nothing at stake but it was a good Clasico, high intensity and chances.
The 33-year-old, who will leave Barca at the end of the season, played 58 minutes before being replaced by Paulinho, departing the Camp Nou pitch to a standing ovation. "We're not anxious about the final, we're all going to be there".
"We always respect Barcelona but in that play I thought kicking the ball out was not necessary".
Real Madrid appeared to be denied a chance to take the lead when referee Alejandro Hernandez failed to whistle a foul despite Marcelo going down in the area after apparent contact by Jordi Alba.
"Clasicos should be played like this, it was a lovely game", Suarez told reporters.
Atletico suffered a hangover from reaching the Europa League final in midweek as they slumped to a surprise defeat at home to Espanyol, with Oscar Melendo and Leo Baptistao on target for the visitors.
"As we are a family, and they didn't want to give us a guard of honour, I've asked our staff to make one", he explained to the crowd.
"Playing as often as we do, we understand that a game like this can happen to us", Atleti coach Diego Simeone said. "We are getting weaker, a bit like my voice".
Deportivo La Coruna won the battle of the other relegated sides, overwhelming bottom side Malaga 3-0.
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