We'll see how things shake out in camp, but even if Couture can't go, I highly doubt Celebrini and Smith will be the top-2 centers with Granlund and Wennberg both on the roster. That's not the way the Sharks have done their rebuild so far (ie preaching patience) and throwing the two rookies into the fire doesn't seem like their MO. I bet one of the 2 vets gets thrown to the wolves with Celebrini as 2C and Smith as 3C in soft deployment. Here's how I see it playing out without Couture:
Zetterlund-Granlund-Eklund
Dellandrea-Celebrini-Toffoli
Wennberg-Smith-Kostin/Grundstrom
Goodrow-Sturm-Kunin
Top line is self-explanatory, solid 2nd line overall and has chemistry from last year. Celebrini gets a scorer in Toffoli as well as a good F1 who is defensively responsible in Dellandrea. Smith gets a center on his wing in Wennberg to help with center duties if needed (+ can score some goals) and a forechecking winger in either Grundstrom or Kostin (I could see Dellandrea here as well with Kostin/Grundstrom on Macklin's wing). The 4th line is self-explanatory...Sturm and Kunin aren't going anywhere even if Kunin sucks, and with Goodrow already initially not happy about coming here, definitely don't want to have him pouting in the pressbox. If Couture can play, he takes Wennberg's role on Smith's wing with Wennberg taking the LW spot alongside Celebrini (with Dellandrea/Grundstrom/Kostin fighting for that last winger spot on the 3rd line).
Defense is more self-explanatory I think...Walman-Benning (or Rutta I guess), Ferraro-Emberson (worked well together last year), Mukh-Rutta/Benning (gives Mukh a veteran partner). Vanecek and Blackwood in net obviously.
Anyway, that's how I see it...we'll see how training camp shakes out in reality.