The Blues boss launches an attack on the London club's onerous fixture list, which will see them play six games in 16 days, including a trip to Russia in the Europa League
The London club's agenda includes two Premier League games, a Europa League fixture against Rubin Kazan and, on Monday, an FA Cup replay with Manchester United, all within nine days.
"Normally, if you have three days between games, you can see the players are tired. When it's two days, it's impossible," Benitez fumed to reporters. "The main thing is using your eyes, your knowledge, the conversations with staff. Then I have to consider the positions of the players - and where the other sides have their key players as well - and prepare the game plan."
He added, "You have to put things together rather than having just one priority because lots of things are an influence, including analyzing the players and the scouts' reports. In terms of trying to prepare the tactics for the United game, that's fine, but physiologically it is much harder. You feel fine the day after a game but the second day is much harder and it will be really tough for everyone."
While United can afford to rest key players against Sunderland on Saturday with its 15-point lead at the top of the Premier League providing a mammoth protection barrier against any slip ups, Benitez understands that Chelsea don't have the depth to match that of Sir Alex Ferguson's side.
Benitez said, "It is impossible to be fully fit for two games. All of them can play, but at which level? Sometimes you can win if you are not 100 percent because you are just better than the other team but that depends on the position of the players who are tired and the opposition."
"Now we have to make these decisions. We know that if we win, it will be that we did the right thing. But if not, we'll be told, 'You made a mistake'."