(CNN) -- Four-time NBA champion Shaquille O'Neal formally announced his retirement from basketball Friday, thanking fans and teammates for their support and saying he looks forward to earning his Ph.D.
"It is now time for me to begin my new life," O'Neal said at a press conference at his home. Dale Brown, who coached him while at Louisiana State University, sat by O'Neal's side.
The announcement was an upbeat occasion, with the athlete thanking his parents for stressing the importance of education, especially if he were to endure a career-ending injury.
O'Neal is completing his doctorate in human resource development at Barry University in Miami.
O'Neal first said Wednesday afternoon that he was going to hang up his jersey. The 39-year-old posted a link to a video on his Twitter account.
In a brief message he said: "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."
O'Neal has been dogged by injuries in the latter stages of his career and played only 37 games for the Boston Celtics this season after struggling with an Achilles tendon problem. He told reporters he did not want the Celtics to have to wait to see whether he fully rebounded from surgery.
The superstar returned for two playoff games against the Miami Heat but managed just 12 minutes, and he told an ESPN reporter that he didn't want to let Celtics fans down.
O'Neal won three titles with the Los Angeles Lakers after forming a devastating partnership with Kobe Bryant, and added a fourth in 2006 with the Miami Heat.
With 28,596 points, O'Neal is fifth on the all-time NBA scoring list and is second only to Michael Jordan on the all-time list of NBA Finals Most Valuable Player Awards. "I'm really going to miss the free throws," he quipped Friday.
He began his career in 1992 when the Orlando Magic picked him first in the NBA Draft and quickly won rookie of the year honors.
O'Neal took the NBA scoring title in 1995 as he led the Magic to the NBA finals, but they were beaten by Houston. He won the accolade again in 2000, when the Lakers won the finals.