Renowned American pitching guru Tom House has openly worked with the likes of Randy Johnson and Mark Prior among other major league pitchers, but Choi's students in the KBO keep their private workouts with Choi just that -- private. They usually come in on Mondays, the league's usual off day, to get their work in without their clubs' knowledge, so as not to risk upsetting coaches on their own clubs who may take offense to outsiders working with their assets.