Chelsea manager Jose Mourinho said he felt his "work was betrayed" following his side's 2-1 defeat by Premier League table toppers Leicester City.
The defending champions suffered their ninth league loss in 16 games as Jamie Vardy and Riyad Mahrez scored for the Foxes at the King Power Stadium.
It leaves the Blues in 16th position, just a point above the relegation zone.
"One of my best qualities is to read the game for my players and I feel like my work was betrayed," said Mourinho.
"One possibility is that I did an amazing job last season and brought the players to a level that is not their level and now they can't maintain it."