The rematch had been set for the March 21 headliner at Maracanazinho Gymnasium in Rio de Janeiro, Brazil, but Assuncao won’t be ready in time.
Having long been lined up for a shot at the UFC bantamweight title, Assuncao broke his ankle in December, which kept him for stepping into a shot at TJ Dillashaw after Dominick Cruz fell out of his challenge for the belt.
That same ankle injury will now keep Assuncao out of the rematch with Faber, according to an initial report from Brazilian outlet Globo.
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Faber won the initial match-up, submitting Assuncao by rear-naked choke at WEC 46 in January of 2010.
There has been no word yet on whether or not the UFC will be able to keep Faber on as the headliner and find him a new opponent, or if the promotion might enlist an entirely new bout to headline the Brazilian fight card.