In 2010, Chao was investigated by the Drug Enforcement Administration for writing at least 108 drug prescriptions to himself, which violated controlled-substance regulations. However, an attorney for a pharmaceutical company that filled the prescriptions said the drugs provided to the Chargers were for use by the team's medical staff to treat players.
The San Diego County Superior Court's website lists several actions filed against Chao since 1998, including by Ryan Leaf and other former Chargers players. It's unclear if any of the cases resulted in judgments against the doctor.
"The NFLPA will take every step to hold the NFL and its member clubs accountable to provide the care that they are mandated to provide," Smith said in his statement. "Dr. Chao's previous medical liability issues only increases our desire to engage in a thorough and comprehensive credentialing process to determine which physicians are providing care to our players and how they were selected by the teams."