The coach said in an interview with Folha de S. Paulo newspaper published Monday that he almost certainly won't pick both players when Brazil hosts the World Cup warm-up tournament.
Scolari said he gave enough chances to both players, adding there's a "90 percent chance" that he will select only one of them for the squad.
"I don't think that they will play together," the coach said. "I wasn't able to test both players together in the friendlies we had, because of the different moments that they were going through. It's likely that I will pick one of them and not the other."
Both have been among Brazil's best players in the past decade but faded significantly recently. They started for Brazil in the 2006 World Cup, however only Kaka made the squad for the 2010 tournament in South Africa. Ronaldinho and Kaka were in the World Cup-winning team led by Scolari in 2002, although only Ronaldinho was a starter.
Ronaldinho now appears to have the edge on his former Brazil teammate.
The 33-year-old former Barcelona star has been thriving with Brazilian club Atletico Mineiro, while the 31-year-old Kaka is struggling to earn a starting spot with Real Madrid.
Kaka was picked for Brazil's friendlies against Russia and Italy earlier this year, and the coach said the former AC Milan star performed "as expected." Scolari has also regularly praised Ronaldinho.
Ronaldinho was left out of the squad for the friendlies in which Kaka played. But he was in the team selected by Scolari for the friendly against England in February, the first for the coach since he took charge of the national team again in December.
Ronaldinho was included in the squad that will play Chile in a friendly next Wednesday, but only players from Brazilian clubs were picked. Brazil will also play England and France before the Confederations Cup, and Scolari will use the same squad that will play in the tournament.
Brazil has played four matches since Scolari returned — the 2-1 loss to England, a 2-2 draw with Italy, a 1-1 draw with Russia and a 4-0 win over Bolivia.
He said only a few adjustments need to be made before Brazil opens the Confederations Cup against Japan on June 15 in Brasilia.
"The team is on the right track," he said. "We have a base, a style of play. We only need to make some final decisions, analyze some alternatives."
Brazil is a two-time defending champion at the Confederations Cup, which is played among continental champions plus the World Cup winner and the host nation.
Looking ahead to the 2014 World Cup, Scolari said Germany, Italy, Argentina and the defending champions are set to be Brazil's top challengers.
"Those three, plus Spain, will make it to the final eight," the 64-year-old former Portugal and Chelsea coach said.
Scolari also said that he thinks it would be good for the national team if star striker Neymar decided to join a team in Europe. There's been talk of several top clubs interested in the 22-year-old player, who is touted as the future of Brazilian football, and many in Brazil say he won't reach his full potential until he moves abroad.
"Neymar has been improving a lot in the past few years. He will be even better in two, three or five years from now," the coach said. "If he decides to go, it would be great. It would be good for the national team. But he doesn't need to go."
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