St. Vrain made his major league debut in a road game against the Cincinnati Reds at the Palace of the Fans (April 20, 1902).

He pitched a 5–0 complete game shutout in front of the home crowd at West Side Park.

St. Vrain pitched well during his only season but gave up a lot of unearned runs.

He is also remembered for running the wrong way on the bases; although he was a left-handed pitcher, St. Vrain batted right-handed.

One day, manager Frank Selee suggested he try batting left-handed, and upon making contact with the ball, St. Vrain was confused enough to run to third base (he was thrown out at first base).