San Diego Chargers team doctor David Chao has been "totally exonerated" by three independent doctors in an unanimous ruling after the NFL Players Association had requested that he be replaced, U-T San Diego reported, citing a team source.

Chao lost a malpractice lawsuit last summer and is facing an attempt to have his medical license suspended or revoked. However, the indedpendent doctors found the union's protest without basis, according to the report.

NFLPA executive director DeMaurice Smith said at a pre-Super Bowl news conference on Jan. 31 that Chao's troubles are an example of why the union wants the NFL to set up a system to verify the credentials of all team medical personnel.

"The players of the National Football League deserve to have a doctor that's not been found liable of malpractice. And that's within the last year, by the way," Smith said.

According to online records, the Medical Board of California is seeking to revoke Chao's license and has referred the case to the state attorney general for possible charges. A complaint alleges gross negligence, repeated negligent acts and failure to maintain adequate and accurate medical records.

Online records also show Chao was found liable of malpractice last summer, has been publicly reprimanded by the board and pleaded guilty to driving under the influence.

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.

Information from The Associated Press was used in this report.