I don't get why Smart would have anything to prove.  He is a solid NBA player on a nice new contract.  Just keep doing what you are doing.  Now if he is able to improve, even a little, great.
Last season, Smart took about 20 3PA per week and made about 6.6 3PM (33%).  If Smart can make one more 3PT shot per week, his percentage goes to 37.5%.  Then suddenly not only is he a top defensive player but also a very solid shot maker.  Of course he could go the other way and start to make one less per week.  Point is he is fine and if he improves even a little, he is great.
The only other area he could improve upon is durability, but I am not sure that is going to happen.  But Smart has nothing to prove otherwise, that is why he already got the contract.  He already proved what he needed to prove.