FA Cup holders Chelsea are unbeaten in 25 FA Cup matches (W20, D5), and have lost only one of their last 36 in the regulation 90 minutes
Benitez was the target for loud abuse from Chelsea's angry travelling support as he walked off at half-time with his team 1-0 down - then heard chants of "You Don't Know What You're Doing" when he sent on defender Cesar Azpilicueta ahead of striker Demba Ba with his side 2-1 down.
"I have said before that I am just concentrating on my job. I try to stay really focused and I can guarantee Juan Mata changed the game when he came on," he said.
"The club said they wanted a manager with experience and I will try to do my job."
He said: "In the first half we didn't do what we had to do. We made too many mistakes, but I was really pleased with the reaction of the team after that. We showed quality and character."
Chelsea appeared to be denied a clear penalty in stoppage time when Harlee Dean handled Mata's shot and Benitez said: "We were really disappointed with that not being given.
"It was very, very clear but it is also very, very clear we didn't perform in the first half. We were much better after that."
Brentford manager Uwe Rosler admitted his team were fortunate to escape a penalty award, saying: "We deserved that bit of luck. Harlee Dean did handle but the hand was at a very close distance. There is some football god up there.
"I'm slightly disappointed we didn't win but overall my players did fantastic and deserve a lot of praise. They have earned the right to play at Stamford Bridge. Individually and collectively they were top drawer."
Rosler also clearly thought Chelsea keeper Ross Turnbull was fortunate to only receive a yellow card when he pulled down Tom Adeyemi.
The Brentford boss said: "It was a goalscoring opportunity that was denied and we all know what that means."
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