On the Pens side, if they're using analytics from the regular season or even the previous rounds as a predictive model, they might not be taking into account Daley's injury which happened fairly late, and the fact that the Lightning straight up are weaker defensively and in goal (and also more injured) compared to the Sharks.

If the Penguins played weaker teams and had better stats, it doesn't necessarily translate to their matchup against the Sharks. Only the Caps were a fully healthy threat. The Rangers were not looking so great. And the Lightning would have been stronger with Bishop and Stamkos and a less rusty Stralman.

I don't think the Pens will be a pushover by any means, but just doing a matchup position by position (forwards, defensemen, goal) - the Sharks are both healthier and stronger. Especially the Pens blueline look to be getting pretty thin.