 The Detroit Pistons have agreed to a four-year contract with coach J.B. Bickerstaff with a team option for a fifth season. A person familiar with the situation told the Associated Press yesterday. The Cleveland Cavaliers fired Bickerstaff in May after they lost to Boston in the Eastern Conference semifinals, despite them winning 99 games over two years. The Pistons fired coach Monte Williams one season into a six-year, $78.5 million contract.