Chelsea centre-back Gary Cahill thinks the club's hopes of qualifying for the Champions League are being hindered by what he describes as "ridiculous" fixture congestion.
The European champions lost 2-0 at Manchester City on Sunday to give hope to the teams bidding to pip them to a top-four berth.
Tottenham Hotspur could climb above Chelsea into third place with victory at West Ham United later on Monday, while beleaguered Arsenal are just two points behind Rafael Benitez's side in fifth place.
Sunday's game was Chelsea's 46th this season -- more than Arsenal (41), Tottenham and Manchester City (both 38), and sixth-placed Everton (32).
The Blues' calendar has been swelled by December's trip to Japan for the Club World Cup, while they also remain in contention in both the FA Cup and the Europa League.
It may mean more matches for Chelsea's fans to take in, but Cahill says it is having a harmful impact on the squad.
"Unfortunately, it does take its toll," he told Chelsea TV.
"I think if you look back at the start of the season with the spark and the zip we had -- I think sometimes a little bit of fatigue plays its part.
"We haven't had a clear week for about 29 weeks and you're expecting to go into games feeling 100 percent fresh, trying to push on further in all competitions.
"I think at this stage of the season, it's not an excuse, but fatigue has to play a part. They (Manchester City) had a clear week and we've had a ridiculous amount of games."
There is little respite on Chelsea's horizon, with Wednesday's FA Cup tie at Middlesbrough followed by a league game with West Bromwich Albion and the away leg of their Europa League last-16 tie with Romanians Steaua Bucharest.
"It's something that we have got to deal with," Cahill said.
"We've got the two cups and obviously trying to get the Champions League spot. That's our aim from now until the end of the season. That's our focus. We have to go again. We are still in that position.
"All three are in our own hands so we need to keep going and plug away and make sure we achieve the goals we want to achieve."
Cahill believes the fatigue in the squad was evident in their porous defensive performance at City.
"I had way too much (to do)," he said.
"Normally at a big club, in a game you probably get asked to do three or four important things in a game. (Against City) we probably had 20 or 25.
"Unfortunately, if you keep getting asked the question, ultimately there's going to be a goal."