According to some media outlets, the 41-year-old captain of the Portuguese national team is expected to be sidelined for between two and four weeks, meaning he should be up and running well before the World Cup kicks off in the United States, Mexico and Canada on June 11.

The former Manchester United, Real Madrid and Juventus player "has started a rehabilitation programme and his condition will be assessed day by day," Al-Nassr said.

Ronaldo, who is in line to play in a record sixth World Cup, was injured during a match at Al-Fayha last month in the Saudi Pro League.