The 22-year-old has been sent home from Brazil's squad at the Copa America in Argentina and will be assessed by Spurs' doctors.
Sandro complained of pain after training in Campana and was diagnosed with swelling in both calves, as well as a ruptured meniscus.
No time for rest: Sandro has been with the Brazil squad at the Copa America
Brazil team doctor Rodrigo Lasmar said Tottenham would decide whether the player needed surgery, but warned recovery from the procedure usually takes four weeks.
Tottenham host Everton on August 13 in their opening game of the new Barclays Premier League season.
Lasmar said: 'Last week he initially responded well to treatment, but complained that the pain had returned. He will return to his club for treatment.'
Wise buy: Sandro (right) broke into the Spurs midfield last season
Sandro said: 'It's hard to talk right now because we had plans for a beautiful tournament with my friends and now everything is under water.
'I'm calm. The players gave me a lot of strength and I want to thank them all.'
Brazil have come under fire for drawing their opening two games at the Copa America, against Venezuela and Paraguay.
However, a draw against Ecuador in Cordoba on Wednesday night will be enough to earn Brazil a place in the quarter-finals but only a win would guarantee they don't meet Argentina before the final in Buenos Aires on July 24.
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Source: Daily Mail
Source: Daily Mail