Yarnall made his professional debut in 1924 with the York White Roses of the New York–Pennsylvania League.

He pitched a scoreless inning, and in the top of the 5th struck out in what would be his only major league plate appearance.

During that inning, the Phillies scored four runs to take a 6–5 lead, and Yarnall came out to start the bottom of the 5th.

When the first two Robins batters reached base, he was relieved by Jack Knight.

Both runners came around to score, and the Phillies lost the game 11–9, with Yarnall taking the loss.