I think he was really performing well at the guard spot before he got hurt. He was really key to those big runs Forte was breaking because he was always pulling out in front of them, with Webb and Garza sealing off the left side. At the very worst, he looked like an exceptional starting guard.
I'm not sure I'd want to move him to tackle, but if you're signing a guard, that's the only real option. Makes more sense to me to sign a tackle if you're upgrading the O Line and put that tackle on the left side, but this isn't my plan.