Assistant boss Christian Damiano has told Andrejs Stolcers that he needs to step up a gear if he is to secure regular first-team football.
Latvian international Stolcers, a £2million signing from Shakhtar Donetsk, has made only a handful of first-team appearances for Fulham.
Damiano said: "We all know that Andrejs is a good player. But if he wants to progress he needs to show the type of 200 per cent commitment that Luis Boa Morte shows.
"There is no problem with his physical ability but he often disappears during the game. It is up to him whether he wins a regular place in the first team."