The Mexican- American was beaten by the British fighter on a unanimous points decision after a cagey rematch between the pair.
With other challenges ahead for Joshua, it remains to be seen where Ruiz will go next but he has promised to return to the top of the heavyweight division sooner rather than later.
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In a tweet posted on Thursday night, Ruiz said: ‘I’ll be back stronger. I WILL be a champion once again.
‘I appreciate all the love and support from my true fans. I appreciate the haters as well and can’t wait to prove the haters wrong once again.
‘Back to the gym. Let’s start this journey to the belts.’
Joshua was officially ordered by the World Boxing Organisation to defend his WBO title against mandatory challenger Oleksandr Usyk on Thursday night.
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