Injuries, suspensions and players on international duty at the Africa Cup of Nations have taken their toll, with the Spaniard's side set to play their 40th game of the season at Griffin Park.
"In terms of selection it has to be different, we do not want too many players playing too many games," Benitez told the club's official website.
"We have played nine games a month, we have two in the Africa Cup of Nations, we do not have too many bodies, and we have to change the approach.
"If you play them too much they do not have the physical intensity. The players are a little tired.
"Sometimes with the quality you have you can win games if you are not 100 per cent fit. We have seen players rested and the game after were really good.
"We are playing too many games. Swansea (who knocked Chelsea out of the Capital One Cup in midweek) had played 26 games.
"You can say it is the same in every club, every top side has the same situation. The difference is if you have more bodies you can manage. It is always the same.
"You play a cup competition and you think how you can use different players. If you can keep the level you will progress and have more chances to win trophies.
"With the players you have you can manage the shape of the team, but the style has to be playing good football on the floor with pace and a high tempo. It's what we have.
"(On Sunday) we will try to strike the right balance. We need to deal with a different team in a different pitch but I cannot explain too much about what we do. It's part of our game plan and how we approach the game in terms of tactics.
"We will use different players but the question is how many of these players can you use to keep the level and have fresh legs. We have an idea."