It's not just the one game.
I've been paying close attention to Fleming, despite his limited snaps as an extra tackle/inline TE. From week 1, the kid was a mauler in run blocking. I'm very curious to see what kind of pass protection he can provide, because I was intrigued with certain run blocking aspect of his game.
Right now, his strength is...well, his strength. He's a big fucking guy (6'6, 325lb). When he can simply line up across from a guy and put a helmet on him, he does a good job of pushing people around. As a tackle, the majority of his blocking assignments would be on the DE across from him, so it works well for him.
The weaknesses I've seen is that he has some trouble on first step, and he's kind of slow (which shouldn't be a surprise with his size). Being able to get up field is an issue for him, and that is a pretty big issue in the run game for interior linemen. Because interior linemen need to quickly diagnose blitzes and help blocking assignments on pass protection, quick lateral movement are important and it's something he doesn't seem to be great at.
I don't think he will ever be able to be successful at guard, but I do think with some focus on footwork and play recognition, he can be successful at tackle.