(CNN) Anthony Joshua has long been regarded as the savior of boxing's heavyweight division , but his surprise defeat by Andy Ruiz Jr. in New York on Saturday has suddenly cast new light on the Briton's career.

All the talk before the bout had focused on whether Joshua, previously undefeated in his first 22 professional fights, would next take on a high-profile opponent in Deontay Wilder or Tyson Fury.

Few foresaw the 29-year-old ceding his WBA, WBO, IBF and IBO titles in such dramatic circumstances.

"Anthony Joshua's invincibility has gone now and he is now just a mere mortal," former British heavyweight David Haye told BBC Radio 5 Live.

This is Andy's night, congratulations Champ 🇲🇽 pic.twitter.com/5gE8uFx4MG — Anthony Joshua (@anthonyfjoshua) June 2, 2019

With a defeat pinned against his name, the prospect of a fight between Joshua and the unbeaten American Wilder won't bear the same luster it carried before.

The defeat via a seventh round technical knockout is a huge blow to Joshua's brand. This was his first fight outside the UK, a chance to attract new fans and new suitors in the hallowed setting of Madison Square Garden.

Technically, questions will also be asked. Ruiz's quick hands and ruthless counter punching exposed Joshua's defense, flooring the Briton on four occasions -- twice in the third round, and twice again in the seventh.

Ruiz was given an 11-1 chance of winning in New York, but defied his outsider status to be crowned Mexico's first ever heavyweight champion.

Rarely one to speak in inflated terms, Joshua was magnanimous in defeat.

"Boxing's a tough sport. I trained hard, I stayed dedicated, but I got beaten by a good fighter tonight," he said after the bout.

"It will be interesting to see how far he can go so good luck to him ... more life to the heavyweight division."

A rematch in the UK later this year now looks to be on the cards: "Now we'll see what AJ's about," said promoter Eddie Hearn. "At least we know who his opponent is for the end of the year."

Andy Ruiz Jr floors Joshua at Madison Square Garden

Sweet success for Ruiz

For Ruiz, such success is unprecedented.

In his only previous title fight, he lost to New Zealand's Joshua Parker -- who Joshua defeated last year -- but now has four belts to his name.

Indeed, he only agreed to the fight in April after Jarrell Miller failed a drugs test.

"I wanted to prove everybody wrong, all the doubters thinking I was going to lose in the third round, first round," Ruiz told reporters after the bout.

"I was looking at comments as well. But what do you know, man, I'm the first Mexican heavyweight champion of the world ... I'm still pinching myself to see if this is real. It's amazing."

JUST WATCHED Anthony Joshua on his past and present Replay More Videos ... MUST WATCH Anthony Joshua on his past and present 03:17

Ruiz, born to Mexican parents but raised in California, was floored for the first time in his career on Saturday night -- something he said "made me stronger" as he patiently waited for the chance to counter Joshua in the seventh round.

The victory is being touted as one of the biggest in boxing's history, with many drawing comparisons to Buster Douglas' 1990 victory over Mike Tyson.

On top of a plethora of heavyweight belts, it is reported that Ruiz will take home some $7 million from the victory.

That, and a fair amount of chocolate, too.

"Congrats again on the upset ... Victory is sweet, but so is the package we are sending you," Snickers tweeted to Ruiz, who replied "send me a dm [direct message] please. Let's go snickers!!"

For all the questions posed about Joshua's future, 29-year-old Ruiz earned plenty of plaudits following the biggest win of his career.

"I hear a lot of criticism about AJ losing to a fat guy," said former undisputed heavyweight champion Lennox Lewis. "What many don't realize is that [Ruiz] has an extensive and incredible amateur pedigree.

"He still has hands and experience. He's seen it all and it serves him well in the pros despite his weight."

Andy Ruiz Jr. celebrates defeating Anthony Joshua in New York

Meanwhile, Deontay Wilder, who holds the WBC belt, said Joshua "wasn't a true champion. His whole career was consisted of lies, contradictions and gifts," before proceeding on to praise Ruiz.

"A huge congratulations to you @Andy_destroyer1 for your upset win last night," Wilder, who will defend his belt against Cuba's Luis Ortiz later this year, tweeted Sunday.

"You've been blessed to come out of the struggle and to become the 1st Mexican Heavyweight Champion Ever! Wow, that's amazing and I'm wishing you many more blessings to come."