Brazil will want to beat Chile even if it helps Argentina in World Cup qualifying, according to Tostao.
Tite's Brazil have already sealed a spot at Russia 2018 ahead of hosting Chile on the final matchday in CONMEBOL qualifying on Tuesday.
The nation's rivals, Argentina, are sixth – outside even the play-off spot – ahead of a trip to Ecuador, but a win would see them secure at least a top-five finish.
Tostao, a World Cup winner with Brazil in 1970, insisted Tite's side would be desperate to beat Chile, who are also at risk of missing out.
"The sports programs here in Brazil have talked a lot about that. They ask the question if we have to support Brazil or we must support for Argentina to miss the World Cup," he told La Tercera.
"The rivalry with Argentina is very big and everyone knows that, but I can say with certainty that Brazil isn't thinking of helping Chile, or anything.
"Brazil will play for Brazil. They want to win for them, but I think Tite can make one or two changes to test players."
Argentina (25 points) are sixth, but will rise above Colombia (26) or Peru (25) with a win – with the latter duo meeting in Lima.
Chile (26 points) are third, behind Uruguay (28) and runaway group winners Brazil (38), while Paraguay (24) can also sneak in.
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