Jose Mourinho has warned players that being "second choice" at their club could damage their prospects of playing at the World Cup next summer.
The Chelsea manager was speaking two days after Manchester United rejected a bid from the Blues for Wayne Rooney.
The England forward, 27, was angered by a suggestion he could be back-up to Robin van Persie at Old Trafford.
"For a player to be selected for his country, normally he must be first choice at his club," Mourinho said.
The Portuguese was talking at a news conference in Kuala Lumpur where Chelsea officials had told journalists he would not be answering questions about the failed Rooney bid.
But he was happy to discuss how he could motivate his team with the World Cup a year away and was keen to stress a player needed regular football to be certain of a starting place in Brazil 2014.
"He must play very regularly with the club and I think that's the big motivation if they are thinking about the World Cup," Mourinho added.
"So any player that wants to go to the World Cup, if they are a second choice in their club, they are in trouble... they are in trouble.
"So I think this is a crucial year for that and probably many national team coaches are worried because they want their players to play regularly in their teams."
The former Real Madrid manager confirmed on Wednesday that Rooney was his only transfer target this summer.
There has been increased speculation about the striker's future this week after Manchester United manager David Moyes appeared to suggest he would be back-up to van Persie.
The Scot said Rooney "had a major role to play", but added: "Overall, my thought on Wayne is that if for any reason we had an injury to Robin van Persie we are going to need him. I want as many options as possible."
Rooney started 31 games for Manchester United last season and was used as a substitute six times - including being demoted to the bench for the Old Trafford defeat by Real Madrid in March that knocked his team out of the Champions League.
The 16 goals he scored for the club in 2012-13 took his tally to 197 in 402 games.