The Mexican headed to Madison Square Garden as a short-term replacement for Jarrell Miller and was pegged as a 25-1 underdog for the championship bout.
But Ruiz shocked the globe, sending AJ to the canvas numerous times before securing the win via technical knockout in the seventh round.
However, Joshua swiftly returned in December to reclaim his belts, with the Brit adopting a completely new game plan that saw him come into the fight much lighter and outbox Ruiz by maintaining distance.
Ruiz pushed for a trilogy fight directly after his defeat to Joshua in 2019, but AJ’s dominance and Ruiz’s lack of preparation meant it never came to fruition.
The 32-year-old has spoken out about his struggles with depression and mental health since the loss, but explained that messages from Joshua helped him to bounce back and return to training.
“I just wanted to crawl under my bed and just hide and eat Cheerios. Again, though, Instagram proved a source of hope. Only this time it was AJ,” said Ruiz, as per the Daily Mail.
“There were a few messages.
“We were just saying that I’d bounce back, that I’m a great fighter.
“I have nothing but love for him. I don’t have no grudges.”
A year on from his last bout, Ruiz Jr is now scheduled to return to the ring next month, with a fight scheduled against Luis Ortiz on September 4.
As for Joshua, he faces Usyk in Saudi Arabia on Saturday night as he looks to become a three-time heavyweight champion of the world.