Valdes replaced Iker Casillas at half-time of Spain's shock 1-0 defeat to South Africa in Johannesburg but limped out of the action with 13 minutes remaining after damaging his calf.
The 31-year-old underwent tests on his return to Spain on Wednesday, where the extent of the injury was revealed.
A Barcelona medical statement read: "The test taken on Wednesday confirmed that Victor Valdes has torn a muscle in the right calf.
"The approximate time he will be out is around six weeks."
Long-serving number one Valdes, who has announced he will be leaving Barcelona at the end of the season, joins superstar Lionel Messi on the sidelines at the Catalan giants.
Messi is also unlikely to play again this year after being ruled out for eight weeks with a hamstring tear sustained against Real Betis earlier this month.
Both players are now set to sit out Barca's final four Primera Division matches of 2013 against Granada, Athletic Bilbao, Villarreal and Getafe.
They will also miss the Champions League clashes against Ajax and Celtic, and both legs of the Copa del Rey last-32 tie against Cartagena.
Barca are currently three points clear at the top of La Liga and are already through to the knockout stages in Europe.