Quoting: aedoran
Rasmussen will most likely be called up as a winger and if they call up someone to play center it will most likely be Veleno. If that's the case I think it's:
Bertuzzi - Larkin - Zadina
Lafrenere - Veleno - Mantha
Actually, I think Rasmussen will be called up as a C, at least initially. He played the last 10+ games in 2018-2019 in DET as a C, and had a positive Corsi. He's played almost exclusively in GR as a C this season (he did take draws on the PP as a C, but played net-front, so he's responsibility was not quite a C there). He'll never be anything more than a #3 C in the NHL (and definitely not manning the PP or PK as a C), but he's way more engaged as a C.
If DET gets Lafreniere, I think your Cs are (in organizational order): Larkin, Fils, Glendening (even though he's been playing a lot of W), Nielsen, Rasmussen, Veleno, Pearson. I suspect Veleno will pass Rasmussen after next season in org order. If they get Byfield, then Rasmussen will move to be a W pretty quickly (he wouldn't be any good as a #4 C), and Byfield would slot into the #2 C spot.