Chelsea midfielder Nemanja Matic has threatened to quit international duty with Serbia unless attitudes change within the national team.
Matic was part of a Serbia side comfortably beaten 4-1 by Czech Republic in Ostrava on Friday, their seventh loss in the last 11 matches.
Serbia failed to qualify for Euro 2016 - the third successive major tournament they have missed - and Matic is deeply frustrated.
"I always try to lead by example but some people don't want to see that," he said.
"The attitude of some players is unacceptable, not just on the pitch but off it too and it was obvious from the moment we got together on Monday.
"I told our coach [Radovan Curcic] there is no point in me carrying on with the national team if things don't change.
"I'd really like to know whether some of my team mates apply the same poor working ethic at their clubs as they do in the national team most of the time."