Simplify the following text for a Grade 11 native English-speaking person.
Original: The San Sebastian tournament of 1911 was `` one of the strongest five tournaments held up to that time '' , as all the world 's leading players competed except the World Champion , Lasker , who was inactive in serious play at the time .
Simplified: According to David Hooper and Ken Whyld , San SebastiÃ n 1911 was `` one of the strongest five tournaments held up to that time '' , as all the world 's leading players competed except the World Champion , Lasker .