Can Trevor Penning play Left Guard?

Almost anyone who plays T can move inside to G.
T have better feet than G that is why so many teams draft a T & move them inside to G.

It is much harder to draft a G & move them outside to T.
It happens occasionally but not often...

Penning has tremendous pancake run blocking skills but this isn't a good reason to move him inside.

As far as the pressures that are now tracked...
If your allowed pressure's didn't force a pick, a throw away, an incompletion, a loss of yardage due to the QB throwing to his check down
they are completely useless stats...

He didn't allow many sacks & that matters.