UFC president Dana White released video of Conor McGregor sparring with former welterweight champion Paulie Malignaggi in advance of his upcoming bout with Floyd Mayweather last week. And on first glance, McGregor looks pretty impressive.

The highly anticipated fight -- you can order Mayweather vs. McGregor on Showtime PPV -- is set for Aug. 26, and the UFC champion at least has the look of a boxer in the ring.

There's only about 20 seconds worth of video (you can watch it above), but McGregor hits Malignaggi with some pretty decent shots and even knocks him to the mat, though Malignaggi insists it was a push down. Mayweather watched the 12-round sparring session, and needless to say, he wasn't impressed. In fact, he said during a Thursday conference call that many of McGregor's tactics were illegal.

"My thought is I think it was real interesting but a lot of illegal rabbit punching behind the head, a lot of stuff was illegal," Mayweather said. "A lot of grappling, a lot of wrestling, a lot of illegal shots. That's just my honest opinion.

"... He had [referee] Joe Cortez in his training, which is a great thing. Even though he had Joe Cortez in his training camp, I still seen him being extremely dirty. My job is not to worry about the referee. My job is to go out there and fight and let the referee do his job."  

"I mean last time I checked, some may call it a knockdown, some may not call it a knockdown. At the end of the day, it only counts once you get under the lights. That's just the gym.

"We are sitting down here judging Paulie [Malignaggi], a guy that's been retired and been commentating and traveling the world and not going to the gym at all going in there with a guy that's just working up. An athlete -- period -- that's just working up, everyday, everyday and obviously it shouldn't have even went 12 rounds."

We can debate the legality of his moves, but the sparring video certainly did its job -- it at least gave the public confidence that McGregor might be able to hold his own in the ring next Saturday.