Arjen Robben has claimed the constant changing of the Chelsea side is 'bad for a player's self-confidence'.
The Dutch winger's remarks come soon after defender Ricardo Carvalho apologised to manager Jose Mourinho for voicing his displeasure at being dropped.
Competition for places is fierce at Stamford Bridge, with Ghana midfielder Michael Essien the latest big-money signing to join the Barclays Premiership champions.
Robben, quoted in The Sun, said: "If you play two or three matches and one match is bad, you are immediately on the bench and that's not good. It's bad for a player's self-confidence because you can't get a rhythm.
"The problem now is that if you have a dip in form or play badly then you are immediately replaced."
He added: "I believe we should build the team round a fixed group and if the policy is to be continuous substitution then I don't like it. I don't know how the manager thinks but I don't like that system."
