Spain coach Vicente del Bosque has warned Chelsea duo Diego Costa and Cesc Fabregas that they are not guaranteed places in his team when they return to the squad after injuries.
The two played no part in Saturday's Euro 2016 qualifier against Belarus, which ended in a 3-0 victory, and will also sit out Tuesday's friendly against Germany after reporting hamstring and groin problems respectively.
But both Costa and Fabregas had played for Chelsea in their 2-1 win at Liverpool, and Del Bosque said he decided not to pick Costa to avoid confrontation. Chelsea manager Jose Mourinho had previously complained that the striker's appearances for Spain had caused him fitness problems.
And speaking at a news conference on Monday as he looked ahead to the game against World Cup winners Germany, the coach said: "As I have said, when a player who comes to us plays well, others that want to get into the team will find it more difficult.
"If I say that Diego Costa and Cesc may find it hard to play I'm not threatening any sort of revenge or reprisal against anybody, it merely reflects a truth about football that we all know. If someone doesn't play and his replacement does well, the other player has to do better to get into the team. But nobody is ruled out."
AS reported that Costa had not been called up for the two games after advice from national team doctor Juan Jose Garcia Cota.
Its report said Cota did not travel to London to examine the striker, but instead based his conclusions on a telephone conversation with Paco Biosca, the medical director at Chelsea, with whom he has had a 12-year professional connection.
Following the controversy over Costa's omission, the Spanish Football Federation has decided to strictly enforce FIFA protocols and will no longer accept medical reports given over the phone.
Instead, players called up to the Spain squad will travel to be examined by the country's medical staff and, if the assessment made does not tally with the report from a player's club, the matter would be taken up with FIFA.
Both FIFA and UEFA guarantee the right of national teams to select the players they wish to, with "any agreement between a player and a club to ignore this obligation forbidden."