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Volk is to small so the striking will not work as well as it usually does for him. I know he is used to being the smaller man but Makhachev is huge compared to him and has the ability to submit him easily if he can get the takedown. Volk will be not be throwing as many punches as he does normally because he will be worried about the takedown. He could lose in the striking because of this threat of submission. I still think Makhachev submits Volk in 2 rounds he will make volk tired and he will stop defending the takedowns and it will be game over.
Since you are talking about Alexander Volkanovski being too small when he is facing Islam Makhachev, but the fact remains that Alexander Volkanovski has a much bigger reach advantage than Islam and that is his strength when he was facing all these fighters at 145 pound division.
He knows to control the distance and strike with every opponents he faced because he is having a bigger reach advantage than the rest of the fighters and he does have a really small neck and hence even submission fighters like Brian Ortega failed to submit him even after having locked in great submissions.
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The only advantage of Volk on this match is striking and his experience because he fought many strong fighter on his career but he will definitely dominated by Makhachev on this fight since this will be a wrestling game. Islam will never let this fight a striking fest and he will surely attempt takedown as much as possible like he was always doing on his previous matches.
I would say, the only disadvantage of Alexander Volkanovski is that he never fought elite level ground fighters as most of his opponents were strikers with BJJ skills but Islam is a wrestler with submission skills and the interesting aspect is how Alexander Volkanovski will handle Islam on the ground.