Simplify the following text for a Grade 6 native English-speaking person.
Original: He suffered serious head injuries and was sidelined for the rest of the season , replaced by Andrea de Cesaris and a returning Lehto who had been replaced at Benetton after injury complications .
Simplified: Wendlinger was replaced by Andrea de Cesaris . After Lehto had been released by Benetton , he drove for Sauber the last two races of the season .