Because Krejci becomes your third line center.
Second, third.. Dont really matter in my opinion. More often than not Krejci will see more ice time, but not by much. Pretty sure their average will be roughly the same.
I think Czarnik and Vatrano could work real well with Krejci. Czarnik's speed and Vatrano's shot, along with Krejci matrix mode.. Could be a solid line.
I was not a fan of Pastrnak with Bergeron Marchand to begin with. Didn't think it would work... But I'm happy to say I was very wrong about that. And now I wouldn't want to break them up unless things go really bad and desperate.
The Backes line though.. Not so sure about. Spooner really needs to step up. Can Backes at C support a line on his own? Definitely do not like Nash on that wing, but he's not coming out of Julien's lineup.. And the other options.. Schaller.. Acciari.. Beleskey off wing. None are very appealing. Heinen or Cehlarik should get a shot at some point.