Dykstra, 50, was charged with grand theft auto and one count of filing a false financial report in October 2011. He pleaded no contest.
After the incident the baseball star attended a drug and alcohol rehabilitation program and was later sentenced to three years in prison.
After a 12-year career with the Phillies and the Mets Dykstra retired at age 33 in 1996.
Christopher Frankie, who wrote "Nailed: The Improbable Rise and Spectacular Fall of Lenny Dykstra," said he was surprised with the court's decision to let him out so early, "because he blatantly disobeyed the court, and a lot of the stuff was very brazen. He was doing it in the full view of law enforcement."
"I hope, for his sake, his family's sake, and the public's sake, that he doesn't return to his criminal past," Frankie said. "I think people in this country really love a comeback story, so he certainly has that opportunity," he added. "But I'm not convinced that's the path he's going to take."