"Big Phil" fired off the warnings as the team re-assembled for the first time since their spectacular Confederations Cup win in June, telling the players there was still a long road ahead until the 2014 World Cup.
He said Brazil's players needed to carefully consider their club careers and go where they were likely to get a regular game, rather than making decisions based purely on financial considerations.
"A player who wants to play for Brazil has to think about the national team and not just think about the monetary side," Scolari told reporters on the eve of a friendly away to Switzerland, the first of the season.
"The spirit we showed at the Confederations Cup was absolutely spectacular. But now it's over and we're on a new path. The athletes have to remember that a lot can happen - players not getting regular games, transfers, players dropping out of favour at their clubs...
"The players know that nobody has made sure of their place. We played well (at the Confederations Cup), but they have to play at their clubs so they can be picked.
"Some players have credit in the bank, but credit can dry up and that is how it has to be," he added.
Five-times champions Brazil won all five of their matches at the Confederations Cup in June, capping their run with a 3-0 demolition of world and European champions Spain in the final.
Their performance resurrected public confidence in the team as they aim for a sixth world title on home soil next year, erasing previous doubts about whether Brazil were good enough.
Scolari said he was especially concerned about the situation of goalkeeper Julio Cesar, who has not settled on his future after playing for Queen's Park Rangers last season.
"I'm worried and he knows that," said Scolari. "If possible, he needs to try and play, it doesn't matter if it's in the second division, third division or tenth division.
"I want to be able to see how they are playing and if they are in the right state."
Scolari said that three or four players in particular were under the microscope.
"I still have three or four situations I have to analyse and consider whether there are players who are better than the ones we have now.
"We have six or seven games to see if it's worth it or not."
He also admitted that winning the Confederations Cup was not particularly a good omen as previous wins were followed by disappointing quarter-final exits at the following year's World Cup.