While the two-time NCAA Division I All-American took McGregor down with relative ease, he could not seal the fight with enough significant ground-and-pound. The Irish striker made the most out of every opportunity he had standing, wearing Mendes down with body kicks in the first round before finishing him with punches in the second.
Though McGregor entered the cage as a favorite with bettors, Mendes' loss was a shock to many pundits. With that in mind, it's worth rewinding the tape and pinpointing what, exactly, went wrong for him.
When all is said and done, the loss came down to one major error on Mendes' part: his bad habit of standing in place while striking.
UFC commentator Joe Rogan said Mendes being frozen in place by McGregor was uncharacteristic of him and possibly a sign the longtime elite featherweight wasn't in proper fighting shape for this short-notice bout. That, for the most part, isn't true. Mendes has a long-standing habit of planting himself in place before an attack, and McGregor made the most of that fact.
Didn't notice it before? Look back to Mendes' second fight with Jose Aldo and watch the middle rounds, particularly the third. After Aldo established that he's nearly impossible to take down, Mendes' offense became almost flowchart-like where he would plant, look for an opening to throw a haymaker and either throw one and miss, get hit or step to his right, plant and repeat the process.
Aldo exploited this by standing in the middle of the ring, pumping the jab and tagging Mendes as he bobbed up and down in place. McGregor, on the other hand, pressured him to the cage, waited for him to plant and then sniped him with either a big left hand or a kick to the body.
Those kicks to the body paid dividends and visibly shaved minutes off Mendes' gas tank. Ten shots in the first round (via FightMetric) made Mendes feel like he had fought four rounds. By the end of the second, Mendes was in punching-bag mode, and he could barely muster up the energy to explode into one of his big punches.
Was this fight Mendes at his best? No, probably not.
The way Mendes lost this fight was not due to a lack of preparation. It was due to established technical errors on which McGregor was able to capitalize. While a hypothetical rematch could go either way, this was a clean win for the new interim featherweight champ.