Chris Coleman has told Collins John that he will have to wait until Andy Cole hits a rough patch before he can secure a place in the Fulham team.
The Holland Under-21 international has largely played the role of understudy to Cole this season and has scored just four goals.
John admitted last month that he is prepared to be patient before he receives the opportunity to stake a claim for a permanent role in the starting XI.
But with Cole performing consistently for The Cottagers, there is no likelihood of John dislodging the former Manchester United ace in the short term.
Fulham boss Coleman admits he cannot drop Cole at present and has challenged John to put pressure on his team-mate.
Coleman also issued a warning to the teenage forward that he needs to improve upon other aspects of his game, if he is to be a regular in the starting line-up.
“Collins wants to play,” said Coleman. “He’s a confident lad who wants to score goals, but I’ve told him that when Coley gets a bad patch and he gets his chance, he has to take it.
“At the moment, we have a striker who plays in the middle and is scoring goals in a team which has been inconsistent this season.
“Coley scores goals and that’s what he’s done since he’s been here. Collins has to shift him, it’s as simple as that.
“He also has to learn that strikers have a job to do when the team hasn’t got the ball, but he’s getting to grips with that.”