"I met with him this morning and he does not want to continue to play football," Chargers coach Norv Turner told reporters Saturday.
Boller, a first-round pick of the Baltimore Ravens in the 2003 draft, played the past two seasons with the Oakland Raiders. Last year for Oakland, Boller played in two games, completing 15 of 28 passes for 161 yards and three interceptions.
The Chargers lost backup Charlie Whitehurst on Thursday when he rolled his left leg during a practice session.
According to the San Diego Union-Tribune, Billy Volek, who had been the Chargers' backup from 2006-12, turned down a contract offer from the team Thursday.
Starter Philip Rivers and Jarrett Lee are the other quarterbacks on San Diego's roster.