The Brazilian full back looked to have been tripped in the area by a Sergio Ramos challenge but referee Miguel Perez waved play on, a decision that Zubizarreta feels denied his side the point that it deserved.
“The images are very clear on that incident, it was a clear penalty to Adriano,” the former Blaugrana goalkeeper said to reporters.
“It deserved to be a tied game, as it was an atypical Clasico, with a lot of intense play. Now we have to recover from this result for the next [Liga] game against Deportivo.
“We are still many points ahead of second place, and we are working every day to build our game. We must always compete, and the sooner we close out the league, the better.”
Barca interim coach Jordi Roura stopped short of echoing Zubizarreta’s sentiments about the penalty incident, telling reporters: “The images are clear, I don’t want to talk any more about it or the referee.
The 45-year-old also derided suggestions that his team was succumbing to fatigue, with now back-to-back losses to Madrid coming on the heels of a 2-0 reverse at AC Milan in the Champions League.
“We're playing several games lately but I don't think it's a physical problem. At least the team played well and worked hard. Matches are won or lost due to punctual actions, but we had control.
"It's difficult to play against same opponent in a few days. They are different competitions but it's always complicated, it's always like that in Bernabeu."
Barcelona is in action next with a league match at home to Deportivo on March 9, before welcoming Milan for the second leg of their round of 16 tie three days later.