Maybin, who was originally feared to be out two to three months or perhaps longer, instead might be able to return in 4-6 weeks after allowing the injury to heal and then going through rehab.
Byrnes told MLB.com that he "thought he was done for the season."
Maybin suffered the injury making a diving catch Sunday against the Los Angeles Dodgers. He played in only 14 games last season after suffering a torn posterior cruciate ligament in his left knee and having surgery on his right wrist.
Signed to a five-year extension worth $25 million prior to the 2012 season, Maybin has 70 stolen bases in two-plus seasons for the Padres, including a career-high 40 in 2011.
The Associated Press contributed to this report.