updated 11:06 p.m. ET May 12, 2009

LOS ANGELES - A former associate of NBA star O.J. Mayo has told Yahoo! Sports that Southern California basketball coach Tim Floyd paid to help get Mayo to play for the Trojans.

In a story posted Tuesday night at Yahoo! Sports, Louis Johnson, the former associate of Mayo’s, said Rodney Guillory told Johnson that Floyd had given Guillory “a grand.” Johnson said he was able to view $100 bills inside an envelope Guillory had.

Johnson's attorney, Anthony V. Salerno, said the NCAA believes Johnson.

“That’s really the whole thing: who do you believe?” Salerno told The Associated Press on Wednesday. “Tim Floyd had a motive to pay O.J. Mayo to get there. Louis really doesn’t have any motives. He doesn’t have an ax to grind against Tim Floyd.”

Johnson said the payment occurred in 2007. Guillory is a confidant of Mayo’s; last year, Johnson accused Guillory of providing Mayo with improper benefits from an agent while the guard played for USC.

Yahoo! Sports reported Johnson has told NCAA investigators and federal authorities — including the FBI, IRS and U.S. Attorney’s Office — that Floyd paid Guillory.

If Floyd did pay Guillory for delivering Mayo to USC, that would be a major NCAA violation.

Yahoo! Sports also reported that Southern California is the subject of an NCAA investigation into alleged improprieties in both the football and men’s basketball programs.

The football probe stems from allegations of 2005 Heisman Trophy winner Reggie Bush receiving improper benefits for a sports marketing agent while at USC.

Guillory and Floyd declined to comment to Yahoo! about the latest accusations by Johnson.

USC general counsel Carol Mauch Amir also declined comment.

The NCAA does not comment about ongoing investigations.

Johnson had described Guillory as a “runner” who steered Mayo to the Bill Duffy Associates (BDA) sports agency. Johnson said Guillory received between $200,000 and $250,000 from BDA Sports for his efforts, which resulted in Mayo initially signing with BDA when he left USC after one season for the NBA in April 2008.

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Mayo had switched to agent Leon Rose before he was drafted third overall by Memphis last year and was runner-up for the NBA’s Rookie of the Year award to Chicago’s Derrick Rose.

Johnson’s attorneys, Anthony V. Salerno and David Murphy, confirmed to Yahoo! Sports that Johnson had told FBI, IRS and U.S. Attorney’s Office investigators on May 28, 2008, about his account of the payment from Floyd to Guillory. Two weeks later, Johnson told the NCAA, according to the attorneys.

Salerno told Yahoo! Sports that Johnson’s account to federal authorities carried the threat of potential prosecution if Johnson was found to be lying.

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