That is just it, I don't know if holding starters out of preseason makes it more likely they get injured at some point or less likely. There are probably analytics on that. Last season it worked out well relative to injuries, so far this season, not so much.
It is pretty clear what Vrabel's thinking on this is. I can't say he is wrong, I really don't know. It seems like the team would be more ready for the first 3-4 games if the starters played some. But they may also still be 2-2 but with a couple more injuries.
I think in any case, the team should be more ready for the start of the season than it has been the last couple of seasons under Vrabel. Whether that means playing starters some in the preseason, practicing/preparing otherwise differently, whatever. I don't feel it is unrealistic to expect him to have the team more ready for the start of the season. The difference between 2-2 to start and say 3-1 could be a playoff home game. Or the ability to rest some starters the last week of the season.