FRANKFURT, June 11 (Reuters) - Costa Rica defender Gilberto Martinez is out of the World Cup with a knee injury, a team official said on Sunday.

The right back aggravated a knee injury during his side's 4-2 defeat by hosts Germany on Friday in their group opener.

The 26-year-old, an ever-present for his country at the 2002 finals, has returned to his club side Brescia in Italy for assessment.

Costa Rica play their second Group A game against Ecuador in Hamburg on Thursday. Poland complete the group.