Antonio Conte believes Chelsea's gruelling schedule and a lack of squad depth are to blame for the champions' recent struggles.
Conte's side lacked energy and drive as they were forced to settle for a dour 0-0 draw against 10-man Leicester at Stamford Bridge on Saturday.
For the first time in the club's history, Chelsea have endured three successive goalless draws after an FA Cup stalemate at Norwich and a League Cup blank against Arsenal.
Even the 68th-minute dismissal of Leicester defender Ben Chilwell for two bookings in quick succession couldn't lift lethargic Chelsea, who were out-played in the first half and couldn't make their numerical advantage count at the end of the second period.
With an FA Cup replay against Norwich looming in midweek, Blues boss Conte is concerned by the signs of fatigue following the draining Christmas and New Year fixture pile-up.
"We played with tiredness. We suffered a lot in the first half and at the start of the second half," Conte said.
"We played a lot of effort against Arsenal on Wednesday, then to play a really good team in good physical form like Leicester was difficult.
"We played with almost the same players as against Arsenal. I saw a lot of players very tired. I saw Eden (Hazard) was very tired so he came off.
"When I decided to put fresh energy on with Willian and Pedro, the game changed. We created chances to score but at the end the result was fair."
Conte hinted Chelsea's energy levels are affecting results because he doesn't have the quality players in reserve to keep his team fresh and performing at a high level.
The Italian has spent much of the season grumbling about the lack of signings made by the club's hierarchy since he led Chelsea to the title last season.
"I'm doing rotations. Against Norwich I made nine changes, against Arsenal I made 10 changes," he said.
"To face all competitions is not simple. You must have a big squad to do this, otherwise, you take risks to lose against teams like Leicester."
- Room for improvement -
Regardless of Chelsea's fitness problems, Conte's hopes of a strong start to 2018 have also been hampered by their lack of cutting edge.
Four successive draws in all competitions have featured Chelsea missing a host of chances to kill off opponents, with Spain striker Alvaro Morata completely out of form.
After scoring regularly at the start of his first season in England, Morata has netted only three times in 14 appearances, with no goals in his last five matches.
But Conte is adamant Morata isn't the only one to blame for Chelsea's profligacy.
"The problem is for the team, not only for Morata," he said.
"Compared to last season we are conceding less, we are showing great solidity defensively. At the same time we're showing not great quality in our finishing.
"We have to improve if we want to score and we want to win. If you don't score, you're lucky the game finishes 0-0."
With no end to the fixture crunch in sight, Conte must hope the hamstring injury suffered by Gary Cahill is not severe.
"Cahill was a muscular problem, but not a serious problem," Conte said.
Meanwhile, Leicester manager Claude Puel remains confident Riyad Mahrez's fine display won't be one of his last in a Foxes shirt.
The Algeria winger has been linked with Arsenal and Liverpool, but Puel said: "We can see he is enjoying his football, he is happy in playing, in training, he is happy with us and his team-mates.
"There is a lot of speculation about the players, but of course we are happy with him, and we want to keep our best player."