Chelsea boss Guus Hiddink admits several of his senior players could be on the move in the summer.
Hiddink revealed: "There are many clubs where players start playing well in April and May because they know that maybe they want to stay.
"You can see that in the whole history of the game, when players start playing well at this time of the season.
"Generally speaking, even if a player’s contract is expiring, he has a responsibility to deliver."
He added: "I can have an influence on what happens to these players and I can always make suggestions to the people at the club who ultimately decide.
"When players are committed, you don’t worry whether they are 31 or 32. In the longer-term strategy for the club, you must have plans for the future even when a player is doing well at 31.
"You must have plans on what can be done, whether to replace a player in a year or more.
"If people ask me I will give my opinion, whether that is the staff, the medical people, the physios, the guys who practise with the team or the conditioning coaches."
