I do think Marcus Smart is a problem. Issue I see is that he regularly alternates between Bruce Banner and The Hulk, and you never now which one you're going to get. One moment he's Bruce Banner - making the intelligent passes, making the smart plays, doing what he does best. Then next minute his emotion takes over and he turns into the Hulk, charging around the court mindlessly and recklessly, leaving a trail of disaster behind him.
We have two < 25 year old stars on this team who are incredibly talented, but are still learning how to lead a team, control their egos, and play the game the right way. I don't think it helps their cause when you have a guy like Smart who is so volatile and wildly inconsistent.
That being said, a few years back (in the IT4 years and our first season with Kyrie) we had Smart, Brown and (in some years) Tatum on the roster, and this team had a very different identity. Sometimes it felt like they didn't have enough talent to get over the top, and sometimes IT / Kyrie could be a bit ball-hoggy, but the team NEVER could be criticised for lack of heart or lack of effort. They always looked to be playing hard and leaving it all on the floor. They always looked like they WANTED to win. And to be fair, we did have Brad coaching then too and Ainge at the helm. So I really don't know what has changed.
This year we got a tougher new coach, specifically brought in guys who are more physical, scrappy and defensive oriented...yet somehow thus far it's not clear to me that anything has changed. Makes me wonder if there are some kind of locker room issues between those core guys. I've seen a few quotes about Brown and Tautm - both from others and from themselves - saying things like "they don't have to like each other, they just have to respect each other" - this makes me wonder, is there perhaps some bad blood between Brown and Tatum?
Not only are they both battling for the spotlight as stars on this team, but I've also noticed they seem to have a very different mentality towards other things. Brown for example is extremely outspoken and gets involved a lot in off-court issues (politics, etc) while Tatum seems to keep to himself a lot and doesn't really talk about much outside of basketball and his kid. Maybe they honestly just don't like each other much, and that's causing chemistry issues?