Marchand - Bergeron - Cehlarik
Spooner - Backes - Pastrnak
Beleskey - Krejci - Czarnik
Schaller - Moore - Acciari/Nash/Hayes
I think Cehlarik may be a good fit with Marchand and Bergeron. He's smart, has size, and has a knack of getting to the net which is something, in my opinion, Marchand and Bergeron have missed since Recchi retired. If there isn't any developed chemistry, there's always playing Pastrnak, Heinen, Czarnik, or Vatrano on that line. I think Spooner - Backes - Pastrnak has the making to be a pretty good line. Spooner and Pastrnak have shown that they have chemistry. Backes played well with Pastrnak in the preseason, and the first couple of games of the season while Bergeron was out. Backes opens up the ice because of size while Spooner and Pastrnak can open up the ice with their speed on the wing. If Spooner ends up getting dealt, I could see Heinen or DeBrusk getting the call-up. Vatrano would end up replacing Czarnik on the 3rd line as it would give Krejci a shooter he can pass to. From my point of view, it looks like Beleskey and Czarnik have shown a bit of chemistry with one another these past few games, and hopefully that would carry over with Krejci who Beleskey has played with.
Sure Krejci or Backes would be centering the 3rd line, but look at the Penguins who have Malkin, Crosby, and Kessel playing on different lines and all average 18+ minutes. Good players will get their ice time whether it's on the PP, PK, or in certain situations late in the game. I also think it's something that will eventually happen given the amount of prospects the Bruins have on the wing.