Yuu is a play on the shonen protagonist that is good at everything he tries with little effort but gimped by how the expectations placed on him created depression and anxiety that weighed him down and limited his potential. He'd pretty much be a shonen sports protagonist in any sport he went to, he just happened to go into tennis. So... yeah, if he went into volley, their team would be a lot stronger. Even Haruki remarked that in a single afternoon focused solely on trying to become a better blocker, Yuu went from being a total amateur to actually giving Haruki (an experienced player who is among the top spikers in their prefecture) trouble.