Simplify the following text for a Grade 5 native English-speaking person.
Original: McCormick was a professional footballer who started the 2003 -- 04 season at Plymouth Argyle as a backup for Romain Larrieu , but when Larrieu sustained an injury to his cruciate knee ligaments , he soon proved himself a competent replacement .
Simplified: In the 2003\/04 season , McCormick played when Romain Larrieu could not . Larrieu injured his knee .