Iowan Nick Collison of Oklahoma City Thunder retires after 15 seasons in NBA

After 15 NBA seasons, Iowan Nick Collison is retiring from professional basketball.

The Iowa Falls prep star first made the announcement Thursday in a story by ESPN's Royce Young.

"I started in cold gyms in small towns in Iowa and ended up playing in more than 1,000 games over 15 years in the best league in the world," Collison said. "I've had an incredible run. I'm proud of my career.

"But it's time to go. I'm retiring from competitive basketball."

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Collison, 37, led the Cadets to back-to-back state championships in 1997 and 1998. He later went on to play at the University of Kansas, where his No. 4 jersey is retired. 

Collison was selected 12th overall by the Seattle SuperSonics in the 2003 NBA Draft. He spent his entire 15-year NBA career with the franchise, which moved to Oklahoma City in 2008. He played in 910 regular-season games with 177 starts, averaging nearly six points and five rebounds per game.

Later Thursday, he posted a video on his official Instagram account, showing highlights that ranged from his childhood playing days up to his professional years. 

"Today I’m retiring from the NBA after 15 seasons," Collison's Instagram post read. "There have been so many people in Iowa Falls, Lawrence, Seattle, and OKC that have helped me along the way. I can’t really find words to say to my family here so I wont try. I will do my best to let all these people know how much I appreciate them.

"I love my teammates. I will miss the moments with them most," his post continued. "Thank you to the fans that have supported me and our teams all these years. I got to feel the love for a long time. I am grateful.

"It’s my time to go. I got to be here for a long time. I’m looking forward to what comes next. THANK YOU!"

You can watch the video here:

Oklahoma City was eliminated by the Utah Jazz in the first round of this year's NBA playoffs. Ahead of the Thunder's regular-season finale, star point guard and reigning NBA MVP Russell Westbrook addressed the crowd and asked it to show Collison, aka "Mr. Thunder," some appreciation.

"He's done so much for me and for this organization," Westbrook said. "I just want to make sure you guys give him a standing ovation for the things he's done for this city."

In a statement, Sam Presti, executive vice President and general manager of the Thunder, said Collison "has helped define the standards we work by on a day-to-day basis, on and off the court and has become synonymous with the Thunder shield."

"He is a craftsman; tough, selfless and humble. He brought the best of himself his entire career each day he walked through the door," Presti said. "As result of his consistency and longevity, his contributions to our culture and community will have a lasting effect. That is rare in any industry, but especially professional sports.

"Many thanks to Nick and his wonderful family for being such an important part to writing our history and helping to set the course. In doing so, he has set the standards for professionalism and consistency for the years ahead and therefore, will always be part of the Thunder.”