The Spain international added two first-half goals to the Champions League double he scored against Nordsjaelland in midweek to end a two-month wait to find the back of the net in the domestic competition.
But more importantly, he demonstrated a confidence - his second came from his first ever Premier League penalty - to leave Benitez purring.
He said: "It's fair to say that we are watching now a Fernando with more confidence and with more belief and at the same time the team is the same way.
"I was analysing his movement before and we were adjusting little things. It's a question of confidence and just little different movements.
"I have said before, if the team plays well and creates chances, Fernando will score goals."
The win took third-placed Chelsea to within seven points of leaders Manchester United, although having played a game more, and was just what they needed ahead of their departure to the FIFA Club World Cup in Japan.
But they will travel without midfielder Oriol Romeu, who returned to London to have an ankle injury assessed.
Benitez said: "It's always important to win, but especially if you are going to a tournament like this.
"Every day in training, we have seen this on the pitch and for the confidence of the team it will be fantastic, not just to win, but to win in the way we have won the last two games, with a lot of security on the pitch."