After Rodrigo De Paul's opener, Antonio Candreva converted a penalty with a Panenka chip and debutant Ernesto Torregrossa headed home the winner.
Ranieri joked about Candreva's penalty: “I said they're trying to kill me! I went to the team doctor and asked for a check-up!"
He continued: “De Paul is a truly complete midfielder and he is the heart and soul of Udinese, so we had hoped to give him as little service as possible, but he's very good at escaping.
“Udinese were doing what we expected in the first half, going on the counter with pace. We were very organised, but a bit too deep with our wingers, and I didn't want to leave Fabio Quagliarella so isolated. Unfortunately, we got very little service to him.
“I saw Udinese were controlling it too much, so the only option was to throw on two fresh strikers and mirror their tactical set-up.
“I had told the four defenders to stay back and not concede. When we moved to three at the back, I told them to stay there, so we'd push up more with the wing-backs."