In short, yes. Diaz has pretty solid chin. This fight will be competitive as long as Diaz was/is in remotely good shape. I don't think he's lost his fundamentals.
I rewatched Mcgregor/Holloway and I attribute the fact that it went to decision to Holloway being a taller opponent with more reach than Conor is used to. And he survived McG's crosses.
Diaz is a bit taller than Holloway and has an even longer reach. Chin should be on par if not better. This will be no walk in the park for Mcgregor if Diaz stayed conditioned. Fuck the stockton slap; if he gets dazed with even one punch, he's going to get hit with 2 more back to back. Diaz is pretty accurate and can pour on relentless pressure. I'd bet on McGregor, but I'm still excited for this fight.