Gaudette isn't really a center and they don't need one since Compher, Kadri and Mack/Landeskog make up their top 3 Cs. Demko doesn't have much value to them since they have Annunen for the future. Grubauer and Francouz don't need to be replaced, they are playing very well.
They aren't afraid of playing people on their off-wing and several wingers already are. Nichushkin and Burakovsky are both lefties that are playing the RW right now, they can play both sides. They have a need of a top 6 winger and top 9. Some people expect them to go for Toffoli for the top 6, who they were heavily rumored to be interested in during the season.
Overall Virtanen would be a nice add for them. A top 9 winger in their age group.