Sandro out for at least three months
The 22-year-old was forced to withdraw from his country's Copa America campaign on Tuesday with scans confirming he had torn his lateral meniscus and suffered a calf strain.
"The [knee] specialist has advised a three-month rehabilitation period before a return to full training," Spurs said on their website.
Sandro began his career at Tottenham almost a year ago after joining the club from Internacional.
Spurs start their Premier League campaign at home to Everton on August 13.