Now, he's helping a 10-year-old boy named Spencer smile and stay positive as the child endures treatment on his ailing heart.
Green joined Celtics head coach Brad Stevens and some teammates on a recent trip to Boston Children's Hospital, where Green connected with Spencer and the two became friends with similar scars and matching optimism.
Spencer is waiting to be confirmed for a heart transplant after repeated surgeries have failed to do the trick. He says he'll keep smiling, just like Green.
Green credits positivity as the reason he's still in the NBA today. During his recovery year, his determination convinced the Celtics that he would come back strong. They showed their belief in him with a four-year, $36 million contract.
Faith in Green has paid off. In 2013-14, he's putting up his most points as a Celtic (15.9) and is close to his career high of 16.5 points per game in 2008-09 with the Oklahoma City Thunder.
He can now count Spencer among his biggest fans for life.
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