It's a mark he never reached in either of his previous two seasons with the Celtics.
"I was definitely apologetic," O'Neal said. "We can't control our health."
O'Neal's time in Boston was spent more in the trainer's room than on the floor with his teammates.
A left knee injury limited him to 24 games in 2010-11 while a left wrist injury forced him to call it a season after only 25 games last year.
"We had goals of winning a championship and we were built really well to win a championship," O'Neal said of his two years wearing Celtics green.
"When you've been around as long as I've been around, it's hard to win a championship," he continued. "When you get those goals and you can see it but you can't quite get to it and you can't help the team and you know if you were healthy, you could help the team get over that hump.
"There's no doubt in my mind if I was like I am now physically, I would've helped the team in a much bigger way."
Specifically, O'Neal remembers last year's loss in Game 7 of the Eastern Conference Finals against Miami.
"Those games that you know that you could be there and you could be a difference maker," he said. "That is one thing that I wish could've went better."
Despite the disappointment -- both personal and together as a team, O'Neal said he's looking forward to his return.
"The city was fantastic. (Boston is) one of the most unbelievable sports towns that you could ever play in as a professional athlete.
"I'm always going to be grateful to the Celtics," he added, "because they stuck with me through two hard years and didn't blink an eye. It's hard to find that in professional sports now, that loyalty towards players, because it's such a money game and it's such a business."