Steve Johnson retires after 12 years on tour

American Steve Johnson ended his 12-year career on Sunday after losing in a doubles match in the BNP Paribas Open at Indian Wells, Calif.

Johnson and partner Tommy Paul lost a first-round match in straight sets to Wesley Koolhof and Nikola Mektic. Johnson, 34, announced the end of his career immediately afterward.

"It's kind of crazy to think that I've done this since I was 2 or 3 years old and today is the last day I'll compete as a professional," Johnson said. "The tennis aspect, I'm still in love with. I love competing, I love going out there and playing. Physically, I wasn't at 100 percent or anywhere near that the last 18 months, and it took a toll on me."

Johnson was an All-American player at Southern California and won the NCAA singles championship in back-to-back seasons (2011-12).

As a professional, he won four singles crowns and reached a high ranking of No. 21 in the world in July 2016. Johnson won two doubles titles and also earned a bronze medal in doubles in the 2016 Olympics at Rio de Janeiro when he partnered with Jack Sock.

Johnson won over $8 million in prize money.