Diego Costa has admitted he began the 2015-16 campaign out of shape, and that he and his Chelsea teammates are at fault for their awful start to the season thus far.
Chelsea have got off to their worst start in 37 years, having won just two of their first eight Premier League games this season. Manager Jose Mourinho's job security has been speculated about, and many of Chelsea's stars have struggled to match last season's output.
The team currently sit 16th in the table after a demoralising 3-1 loss at home to Southampton at the weekend, and the Spain international says he and his Blues mates are the only ones to blame for the club's current condition.
"We know we're not in the form we were supposed to be at the beginning of the season," he said. "We need to blame the players because we came back from holiday very confident, thinking we could go back into how it was last season, and then realised the team was already in a bad situation.
"I'm going to be very honest: Maybe a few weeks ago, five or six weeks ago, I was not on top of my game. At least physically," Costa told .
"We talk within the players and we know that, maybe at the beginning, we were not 100 percent as we were supposed to be when we got here. I got injured at the end of last season and then I went on holiday.
"Maybe I got out of my diet and, when I came back, I was not the way I was supposed to be. I was a little bit overweight. That affected my game. You can be selfish and blame it on the manager but I'm not going to do that.
"I'm responsible 100 percent, and so are the other guys. So all we can do now is train very hard and work very hard to try to get back to that level where we were the season before."
Amid the criticism levelled at Mourinho for Chelsea's poor start to the campaign, the Stamford Bridge club publicly backed him with their "full support" earlier in the week.
Costa believes the Portuguese is the best man to lead Chelsea through such difficult times, and says the rest of the squad feel the same way.
"He is always giving us all the support we need, and the players talk to each other and say he is the best manager you can have," Costa said. "Always when things don't go the way that everyone expects, people, the supporters as well, always look for someone to blame.
"In some cases they blame the players. In this case they blame the manager, maybe because the manager is Mourinho. Maybe he gets criticised because he is very good. Maybe he gets criticised because he is Mourinho. I have been here for more than a season and have seen sides that have lost many more games than Chelsea, and no one criticises their managers.
"I'm here because I'm happy with the manager but I'm not only speaking on my behalf. I am here to speak for everyone, for the group. All that matters at the end of the day is the group. Yes, he has supported me, but he has shown support for all of the players.
"I have spoken to all of the players and they all feel the same way about Jose. I don't like giving interviews, but I'm speaking for the group. We all feel the same way about Jose."
Elsewhere, Ramires has also said that he and his teammates still have complete trust in Mourinho, despite the club's poor start to the season.