The Devils already have Hughes and Hischier, so they don't need a good 2C. As someone said, they need a 3C who is defensively responsible and can get 35+ points.
The Devils already have Haula who was a good 3C but has regressed because of his age and injuries. They also have few bad contracts such as Palat, Haula, Dillon and Hamilton, so I don't want another bad UFA contract to the team. That's a reason why I don't want them to sign Gourde.
Suter is probably the best option for the Devils if they target a UFA center. He is a good player, but he is also one of the slowest skaters in the league. I'm not sure if I want more slow skaters to the team. Two years ago the biggest strength of the team was their speed, but they have lost it with Noesen, Dillon and other slow skaters.
Ryan Strome might be a good option if the Ducks were ready to trade him. Compher is another one and Pageau third one. On the other hand, those guys are already over 30, so I wouldn't trade Mercer for either of them. I don't want another Zacha for Haula trade where we get only couple good seasons from that player before he regresses.
It's not easy problem to fix, but I'm sure there are still some options available.