"In the past against Manchester United we have played well and had plenty of the ball, controlling the game, but without winning them," said Benitez. "We know they have good defenders, but also we needed to be stronger in attack.
"Torres knows all about the United players and will manage that, because he has a lot of experience and a very strong character.
"I think he could be that extra something which we have needed against United. We are a better squad this season and he is one of the key men in that - and we do have more ways of winning this year.
"It will be difficult, we know that, but I believe that now we have another option that we didn't before. United know he's a good player, they know his quality, and they will be worried about him, that's for sure."
Torres has hit the ground running in his first season in the Premier League and already has 12 goals to his name. It is something that has not surprised Benitez, who insists the purchase of the club's record signing was never a gamble.
"For me it was just a case of calling him and saying: 'we want you to join us,'" said Benitez.
"Another top side was making an offer £6m more than us, and we knew how much he was wanted by others. But Torres knew this club and knew that having so many Spanish players and staff would help him a lot.
"When we decided to sign him I knew a lot about his mentality already. I also knew that physically he would be strong enough to play in England. Yes, it was a gamble, but not a big one because of how old he is."