"We didn't invite O.J. to anything," USC coach Pete Carroll said. "We haven't invited much of anybody. Our practices are open to former players and alums wherever we go. And that's where that stands."
Simpson was warmly received by USC's players when he showed up at Saturday's practice for the game against Iowa. Some have questioned the appropriateness of the visit.
Most of the players weren't yet teenagers when Simpson was tried and acquitted of murder after the 1994 slayings of ex-wife Nicole Brown Simpson and her friend Ronald Goldman.
Simpson, who lives in Miami, was found liable for the deaths in a later civil trial and ordered to pay $33.5 million to the families of the victims.
His Heisman Trophy, won while playing for USC, was sold to pay a small portion of the judgment.
Simpson seemed in high spirits at the USC practice, pumping Carroll's hand and smiling. He hugged many of the coaches and players, including this year's Heisman winner, quarterback Carson Palmer.