A UFC featherweight title unification bout between Jose Aldo and Conor McGregor has been officially booked for Dec. 12 in Las Vegas.

And now that the fight has an official date, predictions on the outcome are sure to follow. UFC flyweight champion Demetrious Johnson shared his thoughts on the matchup during a recent media tour to promote his title fight at UFC 191.

"I'm worried about Aldo," Johnson said. "It's a tough fight. Aldo is a different beast, but we've never seen Aldo fight somebody who comes forward. Everything changes [when an opponent comes forward]."

Johnson (22-2-1) knows a thing or two about defending a title against all challengers. The 125-pound champion will seek his seventh title defense when he faces John Dodson (17-6) on Sept. 5.

Should Johnson beat Dodson (for the second time in less than three years), he would tie Aldo's current streak of consecutive title defenses. The two share a goal of breaking Anderson Silva's all-time UFC record in that category, which is set at 10.

Johnson stopped short of explicitly predicting a McGregor (18-2) win, but he appeared to be leaning that way based on his comments.

"It doesn't matter how hard you train or how good your cardio is -- when somebody comes forward and pressures you and makes you fight, it's a totally different ball game," Johnson said. "When you hit pads, you're not pushing forward. When you're sparring, are you colliding with your training partners and creating scrambles? Probably not, because it's uncomfortable to do that.

"I think Conor McGregor, that's his fighting style. He comes forward. Aldo doesn't really come forward. He almost mesmerizes you with the jab, low kick, inside kick, 1-2. I think Conor is going to force that exchange and we're going to find out who's going to be standing after."

The title fight between Aldo (25-1) and McGregor was originally supposed to headline UFC 189 on July 11, but Aldo was forced to withdraw late due to a rib injury. Chad Mendes agreed to step in for Aldo on two week's notice. McGregor claimed the interim title by defeating Mendes via TKO in the second round.

Johnson said he believes Mendes' conditioning in a short-notice fight played a major role in his performance. Naturally, McGregor has refuted those claims, dismissing them as opinions of "rookies" and "so-called experts."

"From what I heard, Chad Mendes was hunting, traveling, fishing and drinking beer," Johnson said. "They called him with that opportunity and told him how much money he was going to make. I probably would have taken that fight, too. A half-million dollars? I mean, I've never made that before and I've defended the belt six times already.

"I do think [the result] is a little bit of his cardio and having such a short camp to prepare for Conor McGregor. He can say all this talk like, 'Oh, I've been preparing for the guy [for a long time].' No, you haven't. There's a difference. As an athlete and a champion, I know what type of condition I need to go through to be in peak condition. The Chad Mendes that fought Jose Aldo [in October] and the one that fought Conor McGregor are nowhere near the same athlete. Nowhere near it."