The Daily Star says senior Chelsea players have complained several times to Benitez about his training methods.
At one stage of the season they moaned he was working them too hard. Then they argued that sessions were not intensive enough.
Benitez even challenged them about this on Monday – and provoked a passionate outburst from John Terry defending his team-mates.
However, it is also understood there is a split in the dressing-room itself, where there are two opposing viewpoints.
There are players at Chelsea who do not like to see their manager criticised so openly, and others who feel such confrontations could be the best way to bring results.