New Sunderland manager Paolo Di Canio has hit out at the fitness of the squad he inherited from Martin O'Neil.
Sunderland took a shock lead on the stroke of half-time at Stamford Bridge but could not keep pace with the reigning European champions in the second 45 minutes, finally succumbing to a 2-1 defeat.
And Di Canio was quick to identify the root of the malaise which had plagued his team.
"It's not the fittest team in the world," he said. "This team at this moment is not a team that can play Chelsea for 95 minutes.
"In the next few weeks we will do more work and extend the physical condition."
However, the Italian believes his introduction to the club has reinvigorated the players and, with time, will be able to make the changes necessary to stave off the threat of relegation.
"My new team, only a few days together, I've had good answers from them," Di Canio added to the Mirror. "It's typical, some of them have told me what we've done in the last few days has been fantastic. Technical, tactical. They've said that's what we needed.
"We're obliged to give them more energy. We've studied, 24 hours a day, how to give them something more without giving them problems or causing damage."
Information from the Press Association was used in this report.