The Spaniard, who joined the Italian club from Real Madrid this summer, scored the first of their three goals after 32 minutes.
"I'm very happy about the game and also for the goal, but the team and our hard work is more important," he told reporters at a press conference.
"We started a difficult championship well and we want to thank the fans. There are still a lot of games, but we got the three points and that's the most important thing.
"It is always difficult to win. Every team that comes to the San Paolo want to trouble us. But we were calm, we did our job in attack very well and created opportunities and did well together in defence too. When I scored, I felt a huge thrill, I was very happy. We have to continue like this."