WATCH: Demetrious Johnson goes mental after Daniel Dubois’ stunning knockout of Anthony Joshua

Demetrious Johnson has been and will always be one of combat sports' most intelligent fighters, and he's also one of its most ardent fans.

The MMA legend consumes an unreal amount of martial arts content and would often give his instant reactions to big fights no matter the discipline.

His most recent was the heavyweight boxing match between Anthony Joshua and Daniel Dubois.

The British sluggers clashed for the honor of holding the IBF heavyweight world championship this past weekend at the iconic Wembley Stadium in England.

Johnson, who recently retired from MMA, took some time off from his Tokyo vacation with his wife Destiny to watch Dubois stun the boxing world with a fifth-round finish of Joshua.

Ever the social media savant, Demetrious Johnson shared his instant reaction on his YouTube channel Mighty.

He wrote on the video's caption:

"WOW!!!! 'Mighty' Demetrious Johnson INSTANT REACTION to Daniel Dubois' SHOCKING UPSET WIN vs Anthony Joshua at Wembley Stadium!"

Dubois was a +360 underdog in the betting odds and was already seen as another stepping stone for Joshua heading into the all-British collision.

Things, however, never panned out according to the gambling books.

Dubois dropped 'AJ' four times in the match, with the fourth one sending Wembley into a complete meltdown.

Joshua knew he had Dubois hurt with a right cross 40 seconds into the fifth round and he proceeded to pin his fellow British heavyweight to the corner.

Dubois, however, shook off the cobwebs and clocked Joshua with a short overhand right that put the former multi-belt world champion for the 10-count.

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Demetrious Johnson more than happy to transition to BJJ after retiring from MMA

Demetrious Johnson has arguably the greatest mixed martial arts career of any fighter in history.

'Mighty Mouse' retired as the ONE flyweight MMA world champion and holds the UFC record for consecutive world title defenses. He defended the promotion's flyweight world title for a record 11 straight times.

After leaving such an indelible mark in MMA, Johnson retired from the sport earlier this month during the broadcast of ONE 168: Denver at Ball Arena.

In one of his recent episodes of the MightyCast podcast, Johnson explained why he has no regrets about leaving MMA in his transition to professional BJJ.

"But yeah, it's a good decision. I find a lot more enjoyment training jiu-jitsu and competing in jiu-jitsu, just because there's no injuries. Obviously, there's injuries that will come down the line."