For the Bruins, it's Lohrei, Poitras, and DiPietro for me.
Lohrei because he has flashed serious upside at the NHL level and to me it feels like he could easily break out overnight in the right system. It could just be he's forever a third pairing guy though.
Poitras really looked to have turned a corner but only got a brief shot to show it last year, I worry he might break out with another team if we don't give him a real shot this year. He's not likely to ever get to the 2C I thought he could be a couple years ago, but I think there's an NHLer in there in a bottom six role, and probably at center as well.
As for DiPietro, it's because the Bruins consistently develop goalies really well. There's the obvious Thomas-Rask-Swayman pipeline, but look at Vladar who became an NHL goalie after leaving the Bruins system with Calgary and did really well for the Flyers last year, Bussi was the goaltender in the Stanley Cup finals for the Hurricanes, Linus Ullmark got better here (although his time in Ottawa has been uneven), Korpisalo has looked like a passable backup here. Not to mention one of the funniest/most painful, St. Louis loaned Binnington to Providence, he had a breakout season there, and would end up getting called up the following year in St. Louis and be the goaltender winning a Stanley Cup against Boston. There's exceptions, obviously, but still there is a lot of success in taking a goalie from Boston. Meanwhile DiPietro has been one of the most successful AHL goalies in recent memory, winning back to back Baz awards, including winning the Les Cunningham award this year. He is on the smaller side, so maybe it doesn't pan out, but our track record makes me worry if we lose him.