It's a tough poll - I think Roslovic will have a greater impact than anyone else, but he "half broke out" this year already in my books. So the biggest 'breakthrough' I think will be Petan, because they can't send him down and the work he put into his game last year. I wouldn't be surprised if he got some 2nd pp time, and the closest we have on the team now to Thorburn is Tanev, who took big steps forward last year and is actually an NHL quality player...
I would be pleasantly surprised if Niku got PP time over Myers, but I'm also still waiting for Morrissey to get his chance... Not sure what Maurice will do. If I knew he would get time with Buff all year & 2nd PP, he'd be my #1, but I don't believe he will.