He's big, fast, not afraid of contact, good defensively, good shorthanded, was a prolific AHL player, led the league in shorthanded goals. He's smart, he makes clever passes, he can play center and right wing, but he's also light and gets knocked off the puck easily.
He never got confident at the NHL level, he also never really got a stretch in the NHL where he could adjust and get comfortable.
IMO, the Bruins botched his development. The Bruins, under Sweeney, have maintained that a rookie has to beat out a veteran to get a spot in the lineup. And since Sweeney keeps signing free agents it's really effin hard to beat one out. If you're an 'offensive' guy then you have to beat out a top9 guy.
Last summer they told him to add some strength and be prepared to have a good camp. He spent the summer in the gym, added 10lbs, had a great camp... and was sent down because the Bruins had no NHL roster spots, they would have had to waive someone to keep him up. I think that's when they broke him. No matter what he did he wasn't going to get an extended look here. I wouldn't be surprised if he asked for a trade.
He absolutely can be a 3c and after his big season in Providence it looked like he could be a 2c but his development stalled there.