Andy Ruiz Jr has produced one of boxing's biggest ever upsets by defeating Anthony Joshua on his United States debut.Shipped in as a replacement for Jarrell 'Big Baby' Miller, Ruiz Jr was given all-but no chance to defeat the heavyweight world champion, but after a stunning display, and a lacklustre looking AJ, it was a night to remember for Ruiz Jr.In what has been a frustrating spell for Joshua, it's just got so much worse as his American dream has turned into an American nightmare.Going into the fight, AJ was the heavy favourite, and for good reason.Then, moments into Round 3, it was made even more clear why he was the champ after he sent Ruiz to the mat in vintage AJ fashion.

However, unlike the previous 22 fights, Joshua failed to get the job done and seconds later was floored himself.

Moments after that, he was floored again.

Then came Round 7; the end of Anthony Joshua's unbeaten run. Floored twice yet again, the referee called an end to proceedings, leaving the Brit helpless, and the Mexican-American jumping around with joy.

A horrid end to what has been a tricky several months for Joshua and Eddie Hearn.

After defeating Russian Alexander Povetkin back in September, Joshua confirmed plans to fight again at Wembley Stadium on April 13.

However, no opponent was found and the date was eventually scrapped, with Joshua and his promoter Eddie Hearn turning their attentions to a trip to America.

Jarrell 'Big Baby' Miller was the man who got the nod for Joshua's US debut, but after failing three separate drug tests, he lost those privileges and in stepped Ruiz.

Going into the fight, the Mexican-American had only lost one fight, and that was to New Zealander Joseph Parker, who is also the only man to take Joshua the full 12 rounds.

Despite an impressive record, Ruiz Jr was deemed the heavy underdog, but those odds were made to look foolish as he not only held his own against Joshua, but went on to defeat him.

Not only did Ruiz get the win, but he knocked down Joshua a remarkable four times before the fight was finally finished in round seven.

Do not play this down - this is one of boxing's biggest ever upsets.