ORLANDO, Fla. -- Shaquille O'Neal, the man with four rings, 28,596 career points and scores of nicknames, has finally decided to call it quits, ending one of the most colorful careers in NBA history that will surely culminate with a Hall of Fame induction.

O'Neal, 39, announced his retirement Wednesday using the new social media tool Tout, a real-time video messaging service toannounce to fans: "We did it. Nineteen years baby. I want to thank you very much, that's why I'm telling you first, I'm about to retire. Love you, talk to you soon."

"Once a businesman, always a businessman," O'Neal said with a smile later on Wednesday. "I am the emperor of the social media network."

O'Neal said he wasn't prepared yet to reminisce about his long and prolific career, which produced three championships with the Lakers and one with the Heat. "Let's save that for the press conference on Friday," said O'Neal, who will hold that media event at his Isleworth home.

Celtics spokesman Jeff Twiss says that O'Neal has not notified the team of his plans.

"Shout out to @SHAQ on the hall of fame career. One of a kind player," Celtics teammate Rajon Rondo tweeted Wednesday.

O'Neal retires fifth all-time with 28,596 points, 12th with 13,099 rebounds and second only to Artis Gilmore among players with more than 2,000 baskets with a .582 field goal percentage.

LeBron James tweeted: "What a career for Shaq Diesel!! The most dominating force to ever play the game. Great person to be around as well. Comedy all the time!!"

O'Neal signed a two-year contract with the Boston Celtics last summer but a persistent Achilles injury will prevent him from fulfilling the terms of the deal. O'Neal first injured his right Achilles on Christmas Day and was able to play only in two of the final 35 games of the regular season.

On April 3 against Detroit, O'Neal returned to the court after a two-month absence and scored six points in a spirited 5 minutes and 29 seconds before coming up lame and limping off the floor. Although his injury was listed as a strained calf, O'Neal said it was the Achilles flaring up again.

"I felt like someone had shot me in the back of my leg," he said.

O'Neal did not play again in the regular season. He sat out the New York Knicksplayoff series then tried to return in Game 3 of the Eastern Conference semifinals against his old team, theMiami Heat. O'Neal logged 8½ minutes in the 97-81 victory but woke up in considerable pain the next morning. His final game was two days later, when he toiled for three minutes of Game 4 before Celtics coach Doc Rivers pulled him for good.

In the final weeks of the the playoffs, O'Neal, over the objections of team physician Brian McKeon, had "more than five" cortisone shots in his Achilles in an attempt to play against the Heat.

"Doc (McKeon) kept telling me, 'No, no,' but I wanted to play so badly," O'Neal said. "My feeling was, 'If it ruptures, it ruptures.' The Celtics were so good to me I wanted to do everything I could to get back on the court for them."

Throughout his time on the sideline, O'Neal said, he continued to do rehab as well as work on the treadmill and the exercise bike. He swam each evening at the Thoreau Club in Concord and shot a number of late-night free throws in at the Lincoln-Sudbury High School gymnasium across the street from his rented Sudbury home. He lost 35 pounds and was "feeling great everywhere except for that one little spot behind my heel."

O'Neal said McKeon recommended surgery that would "clean up" the area around the Achilles, but O'Neal said the recovery time would be close to nine months.

"I really, really thought about coming back," he said, "but this Achilles is very damaged and if I had it done the recovery would be so long we'd have same outcome as this last year -- everyone sitting around and waiting for me.

"I didn't want to let people down two years in a row. I didn't want to hold Boston hostage again.

"I'm letting everybody know now so Danny (Ainge) and the organization can try to get younger talent. I would love to come back, but they say once the Achilles is damaged it's never the same. I don't want to take that chance."

O'Neal said his final months in Boston included some of the darkest days of his career because "I just hated to let the city of Boston down. I really grew to love the place. Everyone was so welcoming to me and treated me so great. They believed in me and they took care of me, especially the great people of Sudbury. I love that town."

O'Neal also had effusive praise for Rivers, whom, he said, was "one of the best I ever played for."

"I thought Doc was fabulous," O'Neal said. "He stressed 'team' all the time, never wavered on that. He kept everyone together. He's an amazing coach. I want to congratulate him on his five years (extension).

"He deserves it. He loves the organization, loves the players, and we all love him back."

O'Neal is acutely aware the Celtics posted a record of 21-4 when he was able to play 20 or more minutes this season. The chemistry he shared with the Big Three (Kevin Garnett, Paul Pierce and Rondo, he said, will be an enduring memory, leaving him to wonder what would have happened had he stayed healthy.

"We were supposed to win this year but 'supposed' doesn't count," he said. "The path was there for us. All the so-called super powers were gone -- L.A., San Antonio. I really feel if I was on the court we would have done it, but I don't believe in 'ifs.' "

O'Neal will be remembered as one of the most dominant, recognizable and controversial figures in the game, whose body of work included rap records, movies, a lengthy business portfolio and an even lengthier history of philanthropic deeds.

"I tried to make people happy," O'Neal said, "and I tried to have fun. I think I did both."

O'Neal was a franchise-saver when the Orlando Magic made him the No. 1 overall pick in the 1992 draft. He took them from the lottery to the playoffs in two years, and then led them to the NBA Finals in his third year before they were swept by the Houston Rockets.

O'Neal then signed with the Los Angeles Lakers in 1996 and had his greatest success there, winning three titles alongside Kobe Bryant and coach Phil Jackson. But amid tension between O'Neal and Bryant over credit for the team's success, O'Neal was traded to the Heat in the summer of 2004, fresh off a loss to the Detroit Pistons in the Finals.

After 3½ years in Miami, a tenure that included his fourth NBA championship, O'Neal became a veteran-for-hire, moving to Phoenix and then Cleveland and finally Boston. But he couldn't deliver another title for Steve Nash and Amare Stoudemire with the Suns, with James with the Cavaliers or with the Celtics' Big Three of Kevin Garnett, Paul Pierce and Ray Allen.