"Reyes had been struggling with a minor problem from Sunday's league match against Atletico Madrid and, after tests with the national team doctors, it was confirmed he had a minor muscle tear," Real said on the club's Web site on Tuesday.
Reyes has enjoyed an impressive start to the season with Real after completing a season-long loan move from Arsenal in August.
Spain coach Luis Aragones could call up a replacement with Celta Vigo's Borja Oubina, Villarreal's Cani or Valencia's Jaime Gavilan among those pressing for a place.
Spain are joint second in Group F with three points from two games, three adrift of leaders Sweden after losing 3-2 away to Northern Ireland last month.
After the match against Sweden in Solna, Spain face Argentina in a friendly in Murcia next Wednesday.
