Alvarez is a better grappler than McGregor, but the question is that will he stick to a calculated game plan and just beat him by grappling.
Nate is a 155er who took the first fight on 10 days notice, but since he didnt have time to cut weight they accepted the bout at 170 and he made McGregor submit in the 2nd round.
I would say Nate probably had a 10 pound advantage over McGregor in the 2nd fight but they make it seem like McGregor beat a heavyweight, he barely won the decision.
Alvarez is using the fact that McGregor got beat by the #5 lightweight contender(Nate Diaz) against him.
Styles make match ups, Nate was a hard match up for McGregor because He couldn't use his reach advantage and Nate can eat McGregor's shots over and over again, Nate is also a very good boxer.
Alvarez like I stated above cannot hang with McGregor in stand up, so his best bet is to be calculated and grapple like he did with Anthony Pettis.
Key for Alvarez to win this fight for me is grappling and I am not talking about submissions.
If Alvarez uses the grinding style where he is constantly leaning on Conor and making him carry his weight:
1) this thwarts Conor's attempts to strike with him, especially negating Conor's speed advantage here. This will also be extremely frustrating for Conor.
2) He is the bigger fighter and this grinding style of grappling when done correctly could be very energy consuming for the fighter being leaned on (especially if this is done on the fence).
3) Utilize his dirty boxing and make it a down and make the fight into a dogfight once into grappling positions such as head clinch or MT clinch.
Reference for this strategy is Randy Couture vs. Brandon Vera.
Winnable fight for Alvarez, but the key is sticking to this strategy instead of getting wild and brawling. If he can stick with this strategy, I see him grinding out a decision or possibly get a finish if Conor gets tired/frustrated/sloppy.