It's not easy bleeding green, writes Nick Kyrgios.

In a new article he wrote for The Players' Tribune web site titled "Why I Bleed Green" Kyrgios details how a kid from Australia became a devoted fan of the Boston Celtics despite the fact he's never even visited the city. Read the full article and see family photos of a young on The Players' Tribune website here.

More: Kyrgios Believes He Can Be Next No. 1

The world No. 20 recalls staying up all night to watch Celtics games from tournaments stops in Portugal and China. Kyrgios calls the deal that delivered his favorite player, Kevin Garnett, to Boston perhaps the happiest day of his life.

"When the mega trade happened in 2008, and we brought in Kevin Garnett and Ray Allen, that might have been the happiest day of my life," Kyrgios writes. "Garnett is like my spirit animal. He’s my favorite player ever. Every guy wants him on their team, but nobody wants to face him. He’s so intense. The way he approaches the game is unreal."

A former standout junior basketball player who owns "like a dozen" Celtics' jerseys, Kyrgios says he's applied competitive lessons he's learned from Garnett and the Celtics to his tennis career.

"As a tennis player, there’s a lot I’ve learned from how insanely competitive KG is — even now, when he’s 39 years old, he’s still a maniac," Kyrgios writes. "He might offend some people, but at the end of the day sport is about winning or losing. Everything KG does, he does to help his team win. How can a guy play in the NBA from age 19 to 39 and stay on top? There’s the only one answer. Competitiveness. Crazy, crazy competitiveness."

Remember when Kyrgios took on one of his tennis heroes, Gael Monfils, in a game of one-on-one? Here's a reminder.