From the Wiki:
At the age of six, -- Kepler started baseball at the Little League level with the John F. Kennedy School in Berlin. Though he received a scholarship at age seven to the Steffi Graf Tennis Foundation, - he decided to choose baseball. Kepler attended John F. Kennedy School, and the St. Emmeram Academy in Regensburg in 2008, where he was able to train in baseball more than the average American teenager.
He played association football with Hertha BSC,[3] and played baseball for Buchbinder Legionäre Regensburg of the Bundesliga, the highest baseball league in Germany.
Seems he really cared about baseball.