The official has provided an update on the Blaugrana talisman's whereabouts, and played down recent speculation about a special Pepe video
The 25-year-old was fresh from netting a hat-trick during the scintillating match at Riazor, but is understood to have abandoned the team's celebrations to visit the infirmary's labour room.
"Right now, Messi is going to the hospital, but it's for a good reason," said Zubizarreta to Marca. "Getting to meet your son is always something good.
"He played the entire match, scoring three goals. He's completely accustomed to the coming, going, travelling with the team and circumstances in a match to play every minute."
The former Spain international then went on to discuss the Catalans' amazing victory.
"We're tired but very happy. This is a crazy sport, and what happens over the course of an entire season just happened during a single match," he said.
The former keeper, nevertheless, criticised the officiating of the referee: "He produced too many cards, but that is as the match official decides to."
Meanwhile, recent reports have claimed that former Barcelona coach Pep Guardiola has stashed away an unreleased video recording of Real Madrid stopper Pepe's misdemeanours against Messi during the recent Clasico.
And Zubizarreta moved to deny rumours that such a compilation exists, whilst putting talk of transfer interest in the Portugal international to bed at the same time.
"We have never discussed any videos, there is nothing else to say. Pepe likewise has never been on the list of potential signings for Barcelona."