Conor McGregor is the undisputed champion of UFC in his weight division and the pound for pound champion in UFC right now - there's no denying that. Nate Diaz is ranked 6th and is a hungry competitor with everything to gain by taking this fight. On the contrary, McGregor has already proven himself and has everything to lose, not that I think he will.
I don't think Diaz, or anyone else can stop him at or around his preferred weight if McGregor gets his way, which he usually finds a way to do. That said, when you're the champion you become the hunted and your every move is analyzed, memorized, dissected and plans are made on to counter your every move. I'm sure that Richard Perez has coached Diaz well for this fight, whether or not it will help is another thing entirely.
If Diaz can last past the second round, there's a small chance that Diaz will be able to win by submission, the last time McGregor lost was by submission and he looked totally unprepared for how to handle the ground game. Maybe he's improved since then, but if Diaz can get him on the ground without getting knocked out in the process, you will find some great value bets there.
My tip: McGregor in the first round by KO