The coach praised his men for taking charge against their favored opponent, but questioned the penalty handed to the hosts.
Los Che took the initiative and went ahead twice at Camp Nou through Daniel Parejo and Pablo Piatti only to be pegged back, but Pablo Alacer turned home to end Barcelona's 25-game unbeaten run at home in La Liga.
"In the first half we lacked aggresiveness but in the second we found it," Pizzi told reporters after the match. "We were more aggressive in the penalty area and provoked errors, which is why we feel like the worthy victors.
"When I spoke about my ambition to win, I wasn’t thinking about a specific opponent. Our opponents are always hungry for victory, but I have no doubt that my players are more ambitious than I am.
"It was an important and necessary victory, and a big character boost. We must translate it into a confidence to win on the field."
The former Spain international was less than impressed with the penalty awarded to the Catalans, however, when Ricardo Costa was judged to have handled the ball in the area.
"I couldn’t see the play on the penalty call, but there are people who told me that it wasn’t a penalty," the 45-year-old commented. "It was another mistake that hurt us, but we won the game. It was a mistake that could’ve been decisive, but I didn't see the incident."
Saturday's historic win at Camp Nou is Pizzi's second triumph to date since returning to the club he represented in his playing career. The Mestella outfit is currently eighth in La Liga.