LOS ANGELES - Southern California defensive back Brandon Ting, whose father reportedly testified in the Barry Bonds case, tested positive for steroids before his surprise decision to leave the team last week, the Los Angeles Times said Wednesday.

The newspaper, citing unidentified sources, said Trojans coach Pete Carroll declined to comment about the allegation.

A message left for Carroll by The Associated Press on Wednesday was not immediately returned. Tim Tessalone, USC’s sports information director, declined to comment on the report.

No telephone listing for Ting was found in Los Angeles and he did not immediately respond to an e-mail seeking comment.

NCAA rules bar athletes who test positive for banned drugs from playing.

Ting’s father, Arthur Ting, is an orthopedic surgeon in the San Francisco area who has operated on several professional athletes, including Bonds. The San Francisco Chronicle reported last month that Ting testified in the perjury investigation of Bonds — who had denied knowingly taking steroids — and turned over his medical records on the player.

A call left at Ting’s office was not immediately returned.

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Brandon and his identical twin, Ryan, are seniors who played mainly as backups and on special teams with the Trojans last season. On Friday, less than a week before the reporting date for training camp, the school said the brothers had decided to give up football to concentrate on a post-baccalaureate program to prepare for medical school.

“We realized it was in our best interests to end our playing careers. We realized we couldn’t balance both if we want to be serious about med school,” Ryan Ting said in the statement.