It's no exaggeration to say that Anthony Joshua rescued his career with his unanimous decision win over Andy Ruiz Jr on Saturday night.

Joshua went into the fight hoping to regain his four world titles and knew that failure would end his time as a top heavyweight.

The Brit went into the fight over 10lbs lighter than their first meeting and with a new style.

This, clearly, was a far more focused Joshua, one who was determined to avoid any complacency - something many accused him of after the first fight.

12 rounds later, he was a unified heavyweight champion for the second time and no one was in doubt over who the better fighter was.

Joshua dominated throughout, winning with scores of 118-110, 118-110 and 119-109.

So with such a comprehensive victory, how did he lose the first fight?

Well, some will point to Ruiz's lack of professional preparation - he came into this one far heavier and, reportedly, didn't join his camp until September.

Joshua, though, has always said that he'd reveal something about that first fight that wasn't publicly known.

And we've had our first explanation as the champ explained he had health issues ahead of the clash.

"I had some issue with my health which I was going through for a long time," he told the BBC.

"I didn't know what was wrong with me. I felt so tired and drained and thought it must be down to training.

"In the changing room before the fight I got a bucket of ice and was putting my head in it thinking 'why do I feel so tired?'

"The responsibilities of being world champion are difficult. All that stuff, feeling so tired, dealing with obligations.

"Now I have energy, I haven't missed a session."

So we don't know exactly what was wrong with Joshua but it appears he was far from at his best when Ruiz beat him.

He certainly looked like a better fighter in the rematch - perhaps that defeat truly was a one-off.