Smart's D is amazing. He is a velociraptor. There is no argument about this.
Offense wise, he's claimed that his ankle affects him. I choose to believe him. More important than his ankle, though, is how CBS wants to use Smart on offense. Smart's usage changed drastically after the Bonner-lovetap game. He went from a 3rd option to a 4th or 5th. Previous to that game, he'd had relatively free reign regarding what he wanted to do in the offense. He took a lot of spot up 3s, tried out his mid-range game, and yes--he even tried to penetrate on a bum ankle that hindered his quickness. Now (after the Bonner game), he only takes shots where he is wide open under the hoop when the defense misses a rotation, when it is late in the shot clock and he's somehow got the ball (happens rarely), and when the team is running on the fast break.
It's easy to say Smart's 0/3 and 3 points doesn't contribute to the Celtics' offense, but if you watch him out there, he is always in the right spot. He sprints to the corner 3 position and stretches the defense just by being there. He's not super mobile on offense, but when you are both already in your spot and a low priority option for most plays, it doesn't make sense to run through noman's land to get to another spot when the place you are already puts a good amount of pressure on the defense. Smart's campfire in the corner three spot stretches the defense and allows more established players (Turner, IT, Crowder, Olynyk) to get in the teeth of the defense and cause breakdowns/create looks. Putting Smart in the corner 3 makes perfect sense: he's a decent threat from 3 so the other team needs to guard him, but he's not so much of a threat that the team wants run him around in order to generate looks for him. If he gets the 3, he'll take it, but that's not the shot that CBS looks for each possession. Smart camping the corner 3 also allows him to preserve his energy so that he'll be able to keep up the same intensity on Defense. A 0/3, 3/4 FT, rookie Smart doesn't bother me if other guys are getting better looks due to Smart's role on offense. Especially if 2 of those 3 shots are late shot-clock bailout shots.
I think part of the problem is that ET (and Pressey) never pass the ball to Smart. ET seems convinced that once he gets within 15 feet of the hoop, no matter how many people who are defending him, he's the 1st,2nd and 3rd scoring option. He'll do nifty passes under the hoop to people like Bass, and he'll run PnR with Zeller, but he hardly ever looks to kick it to the corner 3, even if Smart is open. I think there are some point guard politics going on, and ET (the Celtics' current """star""") doesn't necessarily love that Smart is the heir apparent.
He'll have a bigger role on offense next year. I can wait for it. He's doing what is asked of him and he's doing a good job of it.