Velocity is overrated. Pedro Martinez had his best seasons once to started taking 5mph off his fastball. Jamie Moyer is still pitching for a reason.
In terms of K's, they will probably be down, Santana wasn't throwing it by people like he used to before the injury anyway, but he was still effective. If he can revert back to that form, you'll have a bargain on your hands. But any time a pitcher comes back from his type of injury, how he will preform is a big question mark, and a small sample size like his in spring training isn't going to have many indicators.
From where he gets drafted he's low risk. Might as well just wait and see. I'm optimistic he'll be fine.