The heavyweight boxing scene has seen some incredible moments of action over the past few years.
In the opening minute of the third round, Joshua demonstrated his power to knock Ruiz Jr off his feet for the first time in his career.
That would have been enough to make this a memorable round, but what happened next was crazy.
The Mexican dusted himself off, and even shrugged off a massive AJ punch immediately after being dropped, and responded with a flurry of punches of his own, which knocked AJ to the ground and sent the crowd into raptures.
Boxing commentator Adam Smith couldn’t believe what he was seeing and described it as an “unbelievable round.”
The shocks wouldn’t end there as Ruiz Jr would go on to win the bout in the seventh round via technical knockout to end the Brit’s undefeated record.
The result is considered one of the biggest upsets in boxing history and has drawn comparisons to Buster Douglas’ defeat of Mike Tyson back in 1990.
Douglas broke Iron Mike’s undefeated record with a 10th-round knockout to become the new heavyweight champion.
Joshua was able to get his win back over Ruiz Jr when the pair faced off in a rematch for the heavyweight titles in Riyadh, Saudi Arabia.
After 12 rounds, the Brit’s hand was raised in a unanimous decision victory.
The 32-year-old will be hoping that he can reproduce this bounce back should he face off in a rematch against Oleksander Usyk.
Joshua tasted his second professional defeat to the Ukrainian back in September inside the Tottenham Hotspur Stadium, losing his WBA, IBF, IBO and WBO belts in the process.
He is hoping to reclaim his titles for a second time should a rematch between the two be confirmed.