Celtics center Shaquille O'Neal missed the team's practice session on Monday due to what coach Doc Rivers suggested was confusion about the reporting time.

Rivers said O'Neal would not be disciplined for the mix-up, but the coach didn't sound pleased about the center's absence on a day the team practiced with 11 players.

"He got the times mixed up," said Rivers. "He missed one, so he owes us one. We're good."

O'Neal joined the team in time for its afternoon flight to Cleveland.

"Yeah [it's frustrating], but you get over it," Rivers said. "Listen, if the guy had a history of something, then you'd deal with it differently. But when the guy doesn't have a history of something -- it happens. It's life, you move on.

"It's not a big deal."