Not sure on this one. I would have picked Khabib without question not long ago, but Conor certainly has a shot.
Mendes is the closest fighter to Khabib that Conor has fought, but they are very different. Chad is better at setting up the TD with strikes, uses his lack of height to get underneath opponents, and his blast double is one of the best in the game.
Khabib has a wide varierty of takedowns and trips. He's a much bigger guy than Chad. His top game is much more unrelenting. He has solid submissions, nasty gnp. He is a much bigger threat than Chad on the ground, but he may have a harder time gettting Conor there. His striking is sloppy and Conor only has to worry about being taken down. That's still a big thing to worry about with a guy like Khabib, but Chad had 1 punch ko power and cleaner striking.
I think Khabib will drown Conor if he gets him down and keeps him down. I could see Conor being able to get a finish possibly even up to rd 4, but if Conor gets mauled I don't see him staging a comeback.
One thing Conor does have is excellent balance. Khabib's takedowns aren't super clean and at times he will be holding onto a leg trying to force an opponent off-balance and onto the mat. Conor seems like a guy who can counter this.
This one could go either way. I am going to go with Khabib though, under the assumption he doesn't fight like an idiot. He will leave openings for Conor at times, but I believe he could be his own worst enemy in this fight; he needs to make sure he doesn't get overly sloppy and overly comfortable on the feet. Conor doesn't need much of an opening. I am picking Khabib via RD 3 TKO.