Responses
I think he's just tired from being really focused on each and every pitching he did from the start since Seihou looks really hard to fight with. Just like the match with Naruta Tech, he got tired after only 98 pitches, which is totally not Sawamura-like first. But I guess paying attention to his grip on the ball and pitching with power, along with strategizing against Seihou's lineup took a toll on his stamina
Especially when the boss entrusted the game to him.
He's sweating because he's hot HAHAHA
On a serious note please don't be injured our baby Eijun.