Baseball-Reference says the NY Giants used Hearn 16 times,all as a starter and the Cardinals used him 6 times as a reliever. If you search for him as a starter, he doesn't show. He shows as a reliever 3 times (Giants only and the two combined). His IP/g is 7.81.
Will I have any problem using him as a starter? I tried him in simulated games and the robo manager pulled him before he finished 5 innings every time.

You can start games with him, but only on a spot start basis. His ip/9 allows him to pitch deeply into any single game effectively, but will drain his seasonal fatigue requiring several games of rest if you do so. I like using him as a tandem starter too

Thanks, that was the answer I was wanting.

His performance history is impressive. 13-15 starts. 55 games played. ERA around 3.0

Wow. Nice find.

for some reason I identify with players like this.