They can mean everything, or nothing. Depends on which athlete you talk to.
For Robert Griffin III, you'd imagine that at this point in his career, he'd wear a Glad ForceFlex our there as long as it didn't read "Redskins." So it's probably extra nice for him that new teammate, wied receiver Darius Jennings, gave up the Browns' No. 10 jersey to accomodate their new quarterback.
Jettisoning a jersey number for an incoming player is a move typically reserved for incoming veteran stars. And those who don't fit in that category usually have to pay in cash or win some kind of competition for the digits.
But hey—Cleveland is accomodating. After all, this Griffin guy could finally turn it all around. Or something.
Dan is on Twitter. He was extremely protective of his No. 4 high school jersey. Which is a very bad number.