Cameroon coach Paul Le Guen has warned his players that he has yet to be convinced by many of them, after their exit from the Africa Cup of Nations.
The Indomitable Lions were eliminated after losing 3-1 to Egypt after extra-time in Monday's quarter-final.
Le Guen will now concentrate on the World Cup, but has put his squad on notice, particularly younger players.
"This would have been a good experience if we had won but there were a lot of players under-achieving," he said.
"It is important for me to be sure I can rely on young players for the World Cup."
Cameroon scraped through to the last eight in Angola before being beaten by the defending champions.
After losing their opening group game to Gabon 1-0, they managed to edge out Zambia 3-2 and contested a tight 2-2 draw with Tunisia.
Le Guen has already proved that he is not afraid to make changes since taking over as Cameroon boss last July.
He stripped veteran Rigobert Song of the captaincy and left defender Sebastien Bassong out of his Nations Cup squad, as well as relegating Andre Bikey to the bench for much of the tournament.
And Le Guen has made it clear that he will not hesitate to replace several members of his squad who made the trip to Angola, as he prepares for a World Cup group which includes the Netherlands, Denmark and Japan.
"I will [now] go to watch a maximum number of games to try to be in a situation where I can select the best players," he said.
"I will also watch games in Cameroon but the best Cameroonian players are competing in Europe."
Cameroon's next game is a friendly against Italy on 3 March.