If he sits 10 games he loses like 9 million bucks, then if he gets hurt in the one of the last 6 (or 8-9) games he hurts his chances of a huge deal.
If he plays week 1 and gets hurt, he gets his entire franchise tag, then has an entire year to recover from an injury, and is more likely to land a big deal than if he got hurt week 15.
Obviously more games would mean greater chance of injury, but it's rare these days for an injury to derail a guy for the rest of his career. It happen, but it's rare.
I still say he does not miss any games, unless he reports so late this week he has to sit week 1 (which is what he probably wants to do, one less game to play while still getting paid).