I've no doubt he could have carried on, there's countless examples of fighters getting hurt and continuing on. Danny Williams got a last round KO with his shoulder hanging out of his socket ffs. Not everyone has that desire though, I think he was just tired (he'd only been 10 rounds once), and disheartened that when he went for the finish it didn't come and his opponent was happy to trade with him. He barely did anything in rounds 8 and 9, he looked totally spent.
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