Rafa Benitez has said Chelsea's recent inconsistency has been caused by the intensity of their fixture list.
Benitez said that was not intended to be an excuse and pointed out that the Londoners have played 40 games since August - more than any other Premier League side - with 20% of those coming in January.
"We're playing a game every three days, more than anyone, and we have some problems with players in the African Cup of Nations and Japan [for the Club World Cup]. Some will say that's excuses, but it's not. It's a reality," the interim manager said.
"In some positions, we have two or three players out. Oriol Romeu is injured, Mikel is in Africa, so we have to manage with Ramires and [Frank] Lampard. So, after two or three games in a row, some are struggling to recover.
"If you have a week, you can recover. If you have only two days and you have to travel, then it can be a problem.
"That is the reason why the team did so well against Arsenal in the first half, and then we suffered a bit because we could not keep the high tempo all the time.
"The problem is for the top sides, especially if you're successful... Reading have played 13 fewer games than us or something."
He said "injuries, the Fifa Club World Cup in Japan, the African Cup of Nations" were all problems the club had to manage.
But Benitez revealed that did not necessarily mean that the Blues would be recalling many of the more than 20 players out on loan from Stamford Bridge.
"Each situation is different," he said. "Some players have agreements that had to be decided early [in mid-December].
"Others are younger players who need time and have to keep working and playing games. That's good for the future of the players.
"Others aren't ready for the first team. We have to analyse each player. It has to be the right players in the right position."