Which Penguins' prospect is most likely to make the opening night roster?

With training camp about a month and a half away, many Penguins' fans are anticipating what the roster could look like come opening night.

Potential trades aside, what about prospects?

There are several who should be in the mix - aside from Sergei Murashov, who appears to be a relatively obvious shoe-in - for an NHL roster spot, including Rutger McGroarty, Ville Koivunen, Harrison Brunicke, Owen Pickering, Tristan Broz, and Avery Hayes.

Which is most likely to make the NHL roster? Is there someone else?