"But if it does happen, Eddie is a big boy. He can grapple. He's a f***ing grinder and whatever endurance issues Conor may have, he better iron those f***ers out before you go to town with that guy."
Alvarez, a former Bellator champion, won the 155-pound belt by upsetting Rafael dos Anjos in Las Vegas in July.
After finishing the Brazilian via first round TKO he immediately called out McGregor. "I would ask Dana White to give me an easier fight like Conor McGregor," Alvarez said. "I deserve that, I've been fighting the best guys, so I would like a gimme fight, so Conor, I more than welcome that."
At the time, McGregor was busy preparing for his rematch against Nate Diaz at UFC 202, a fight that was fought at 170 pounds that he won by decision. If he now chooses to fight in a third weight class in the UFC, Rogan has his doubts.
"I don't think it's an easy one at all. I don't think Eddie's the best match up at all," Rogan said. "First of all Eddie's known for having a chin and known for being able to bounce back from getting hurt - he's got massive heart. And he fights at his best when the chips are on the line - like in the dos Anjos fight."
Schaub also queried McGregor's ability to compete in the lightweight division, which after Alvarez has a top five of Khabib Nurmagomedov, dos Anjos, Tony Ferguson, Diaz and Edson Barboza.
"If you look at the top five, none of them are easy at all," Schaub said. "The future doesn't look great at 155."
But Rogan disagreed saying McGregor showed against Diaz he could handle a larger man. "I can't say that," he responded. "Nate is clearly one of the best at 155 ... so Conor just beat him. It was obviously a very close decision but I think it was probably a fair decision."
The match-up against Alvarez flies in the face of Dana White's previous demand the Irishman return to defend his featherweight belt after UFC 202.
It could be an indication the UFC boss has softened on that stance or an admission McGregor no longer has the ability - or desire - to make the 145-pound weight limit and is destined to continue his career at 155 pounds.
"I don't think he can make 145 any more," Rogan said.
"Me neither," added Schaub. "His camp says he can't either."
Rogan: "I kind of want to see him rematch Aldo though." It appears that will have to wait.
MOOTED FIGHTS FOR UFC 205
Eddie Alvarez vs Conor McGregor (lightweight championship)
Tyron Woodley vs Stephen Thompson (welterweight championship)
Chris Weidman vs Yoel Romero (middleweight)
Donald Cerrone vs Kelvin Gastelum (welterweight)
Tim Kennedy vs Rashad Evans (middleweight)
Gian Villante vs Marcos Rogerio de Lima (light heavyweight)
Liz Carmouche vs Katlyn Chookagian (women's bantamweight)
