この犬はまだ甘い毒を知らない

Matsumoto is the ace pitcher of the baseball team. Sakaki is a third-year upperclassman who looks after Matsumoto like a wounded dog, having him do his biddings from time to time. Matsumoto finds himself tamed by Sakaki, the lone head of the gardening club, during his rehabilitation period, upon which Matsumoto is allowed to return to the regular lineup. Sakaki congratulates him and tells him that he will be released from his errandboy duties, leading Matsumoto, who's defiled Sakaki many times in his mind, to refuse being let go. (Source: MangaPlaza)