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While Conor McGregor spent the last week going toe to toe with Floyd Mayweather Jr. on the microphone, former world champion Jessie Vargas cast further doubt on whether McGregor can hang with Mayweather in the ring.

In an interview with Villainfy Media, Vargas said McGregor got knocked out during a sparring session in preparation for his Aug. 26 bout with Mayweather.

(Warning: Video contains NSFW language.)

While considered a great striker in a mixed martial arts capacity, many question whether McGregor has bitten off more than he can chew in a fight against Mayweather.

In June, Chris van Heerden shared a clip of himself sparring with McGregor, and the UFC lightweight champion looked overmatched:

McGregor also failed to silence his critics with a training montage he posted to Twitter in June:

Mayweather posted a training clip on the same day and didn't appear to have lost much speed despite spending over a year-and-a-half out of the ring:

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According to OddsShark, McGregor is a 7-2 underdog against Mayweather.

McGregor's months of training should pay off with regard to making him an improved boxer, but he's facing a nearly impossible task of bridging a gap with one of the best defensive boxers in the history of the sport.