5th round picks don't make $1,000,000 or even $500,000 in guaranteed money until
they've proven their ability in the league. 3rd round picks do, though.
Like I said, it depends on feedback. If they tell him he's projected 4th-5th round this year but has a chance to increase his stock by 1-2 rounds next year by showing more as a receiver out of the backfield and as a blocker then he'd be wise to stay.