Guus Hiddink has warned Chelsea's players that some of them could be following him out of the Stamford Bridge door this summer if they fail to convince him they are deserving of a new contract.
Although the Dutchman's short-term contract will expire at the end of the season he will still offer his opinion to the club over those players who are keen to broker new deals.
''There are many clubs where players start playing well in April and May because they know that maybe they want to stay,'' said Hiddink.
''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.
''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.''
Drogba, Ballack and Carvalho are all the wrong side of 30 but Hiddink does not feel age should be a factor.
''When players are committed, you don't worry whether they are 31 or 32,'' he added.
Chelsea face Barcelona in the second leg of their Champions League semi-final at Stamford Bridge on Wednesday having drawn 0-0 in the Nou Camp.
Roman Abramovich's millions have so far failed to help the club conquer Europe and, after last season's penalty shootout defeat by Manchester United in the final, midfielder Frank Lampard admits the pressure is growing.
The 30-year-old said: ''I know what people mean when they say we're cursed in Europe because the more years it comes and you get very close but it doesn't quite happen, the more you start to think, 'Will I ever get there?'
''There's definitely a source of determination because we're all professionals and all playing at a club that craves success and wants success, and you need that as players.
''We've basically achieved everything else domestically, so Europe is the one hanging over us.''