Chelsea boss Rafael Benitez has revealed the number of games his side have played this season is starting is taking its toll on the squad.
The Blues have played more fixtures than other club in Europe due to their commitments in the Premier League, cup competitions and forays in European competitions.
"After every game we see how the players feel, we have all the statistics about the amount of ground covered, but you also have to speak to the player and see how they feel," Benitez told the club's official website.
"Sometimes you have players who you don't want to change because they are a key part of your offensive game. Some players you can change if you have someone in the same position at a similar level, but it depends on the game."
Chelsea take on Manchester City at the Etihad Stadium on Sunday just days after securing their place in the last 16 of the Europa League.
