I mean, so does Purdy and I hear he's pretty darn good. For reference:
Purdy vs Drake: QBR: 29.3
Stanley vs PSU: QBR: 35.4
One of those games was an away game in rain against a ranked team with scholarships. The other was a home game in the rain against a non-ranked team without scholarships.
I think everyone has bad games.
Also, Stanley hurt the thumb on his throwing hand during the game at PSU.