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.