Reds boss Benitez told Liverpoolfc.tv: "When you are a manager you need to make decisions, not just think about them. You must think how you can win the game. Every player is the same for me when you are trying to win a game.
"We have talked because every player would be disappointed, especially Gerrard because it was a derby. He wanted to score the winning goal, but he is okay. After some time he'll understand that it was an idea and I was thinking about the best for the team.
"You know when you change a player he must show that he wants to play, but I think he was okay at the end."
Gerrard, who captained England during last week's defeat to Russia in Moscow, had earlier admitted he had found the decision hard to take despite victory over their derby rivals being "the most important thing".
"I'm a local lad so the derby is really important to me and I would have liked nothing better than to play the full game and to be on the pitch when we got the winner," he told Liverpoolfc.tv.
"But as it turned out I was taken off and Lucas Leiva who replaced me played a crucial role in us getting the winning goal.
"I was hurt and disappointed at being taken off because, like I said, I'm a local lad and the derby means everything to me."