I think Drew looked good in this game. Some of his incompletions were still pretty accurate. Apparently he missed a pre-snap adjustment on the blitz/fumble play. I don't think he made any mistakes after the snap, though, because that pass rusher was able to get to him much quicker than you'd expect , and from the blindside.
Anyway, I'm not gonna read too much into a preseason game. Not sure how much he played against backups vs starrers. Preseason games can make average QBs look like all-pros. Not a huge sample of attempts, either, especially of 10 yards or more.
With that said, I predict Lock will be the starter. And he will be a Pro Bowl QB this year.