Hajime no Ippo, Eyeshield 21 Recommendations
Both the main characters are originally weak, and were bullied at the start of both of these mangas, but then they found strength in a sport that they each love playing.
Hajime no Ippo being about Boxing, and Eyeshield 21 being about football.
They gradually become better at their respective sports and they each overcome their own fears in order to achieve their goals.
Train hard and you will be able to do what seemed impossible. That is the main thought is both of these series. Although they center around a different sport (solo vs group), they goal that both main characters want to achieve is become better in order to beat their enemies and win the championship. To achieve this goal, they have to be stubborn and need to have a lot of determination. The maincharacters will do everything to reach there goal. If you like exciting show-offs and intense training, than both of these series are perfect for you!