Apparently, he injured himself while running third in the Juvenile.

from Bloodhorse:

Two-year-old Street Hero, winner of the Norfolk Stakes (gr. I), has been retired from racing for stallion duty at Tom Simon’s Vinery near Lexington. The son of Street Cry will stand for $12,500.

Street Hero, who won or placed in all six races, squared off with divisional leader Midshipman in his last three starts. After finishing third to him in the Del Mar Futurity (gr. I), Street Hero beat Midshipman in the Norfolk at 1 1/16 miles. The two then faced each other in the Bessemer Trust Breeders’ Cup Juvenile (gr. I), with Street Hero finishing third behind the winning Midshipman. Following the Juvenile, Street Hero underwent surgery for a fractured knee. He retired with earnings of $419,360.

Kentucky-bred Street Hero, who raced as a homebred for trainer Myung Kwon Cho, is out of the graded stakes-placed Summer Squall mare Squall Linda. He now is owned by Cho and Vinery.

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