Edited Dec. 17, 2018 at 12:55 p.m.
As good as Marner and Rielly have been, I can't see team Canada selecting both of them. They are notorious for leaving young skill players off the team in favor of older experienced players and those who have played with the team before. They are especially known to favor an even L/R split on the defense, and as mentioned earlier Vlasic and Giordano both make the team, likely with Keith as the 3rd LHD.
It would probably be something like this:
Marchand* - Crosby* (C) - Bergeron*
Benn* - McDavid(A) - Seguin*
Hall - Stamkos* - MacKinnon
Tavares* - Giroux* - Scheifele
Giordano - Doughty*
Vlasic* - Subban*
Keith* - Weber* (A)
Holtby*
Price*
Extras:
- Toews* (Canada loves him)
- Getzlaf*
- Rielly (LHD)
- Burns* (RHD)
- Crawford*/Fleury/Dubnyk/Whoever
*=Played on a Team Canada before
Meaning the only new additions are McDavid, MacKinnon, Hall, Scheifele, Giordano, Rielly, and maybe the 3rd goalie. Technically Seguin didn't play in the World cup but he was selected to the team.