O'Connor was making his first media appearance since missing the announcement in Sydney last Thursday.
The 21-year-old utility back had been asked by the Australian Rugby Union to explain his absence and could be forced to miss next weekend's Tri-Nations decider against New Zealand in Brisbane - the Wallabies' final match before next month's World Cup - as a result.
"I just want to express my regret as this is such an important event for the Wallabies and I would like to apologise to all the fans and my teammates," O'Connor told reporters.
"I let myself down, I let the fans down and I guess all the Wallabies down and the ARU as well.
"It's a massive event (World Cup squad naming) and one that only comes around every four years."
The ARU is investigating the incident and is expected to make a decision regarding any punishment on Monday.
O'Connor was reportedly spotted at one or two hotels the night before the squad announcement, but he would not reveal the reason for his absence.
"The process is out of my hands. It's with the ARU and whatever the outcome is, I'm willing to cop it," O'Connor added. "All I know is I will do all I can for the team.
"We've got a massive game coming up this Saturday and a chance to win the Tri-Nations before the World Cup, so all my efforts (will go) into training hard and doing what I can for the team.
"I want to be there for my team-mates, as they would be there for me."
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