Last night at UFC Fight Night 51, Andrei Arlovski avenged his 2010 loss to Bigfoot Silva by picking up an impressive KO win in the first round of their 5-round main event bout in Brazil.

We have complied the best Tweets from UFC fighters reacting to the massive upset.

@UFC tonight and supporting my teammate @AndreiArlovski ! Goooo pitbull!

— Alistair Overeem (@Alistairovereem) September 14, 2014

Alright let's go my angry friend @AndreiArlovski time to put in work

— ike vallie-flagg (@IKEVF) September 14, 2014

Let's go @BigfootSilva! #ATTNation #UFCFightNight #UFCBrasilia

— American Top Team (@AmericanTopTeam) September 14, 2014

I said this a couple times this week but pretty wild that Bigfoot, coming off a suspension, ends up returning to the cage before Hunt.

— Ariel Helwani (@arielhelwani) September 14, 2014

That staredown though!!! #UFCBrasilia

— UFC (@ufc) September 14, 2014

Whoa! Big upset in Brasil! #UFCFightNight

— James Krause (@TheJamesKrause) September 14, 2014

YES!!!!!!!!!! @ufc @UFCFightPass

— Julie Kedzie (@julesk_fighter) September 14, 2014

Whoooooooa! #arlovski

— Dave Sholler (@Sholler_UFC) September 14, 2014

Congrats my friend!!!!! @AndreiArlovski

— Cub Swanson (@CubSwanson) September 14, 2014

That was awesome. Great job @AndreiArlovski you put him to sleep. #ufcfightpass

— John Dodson III (@JohnDodsonMMA) September 14, 2014

Oh!!! That's respectfully an upset! Caramba…

— Raphael Assuncao (@RaphaAssuncao) September 14, 2014

HOLY SHIT!!!!!!!! #andrearlovski

— Dana White (@danawhite) September 14, 2014

Congrats @AndreiArlovski !!!!!! WOW

— Dana White (@danawhite) September 14, 2014