If Stango had used the plasmid, he'd be dead by now. As it is, he's willing to twist aside just enough, leaving him with a nasty--but not deadly--gash along his leg. The unexpected movement sends his shot wide, and he snarls more with rage than with pain.

At this distance, he won't be able to avoid a second sweep of the scalpel. Unless...

Staggering a little on his wounded leg and leaving bloody prints on the dirt floor of the maze, he runs at Diogenes again, at the last moment swerving and going past him, turning back to face him once he has a little distance, hoping that the change in direction will slow Diogenes down enough to save his life.