Sakuishi Harold manga
From MangaScreener: A professional baseball manga by Harold Sakuishi, the author of Beck. Taiko Busujima is a powerful young pitcher looking to make it into the Japanese big leagues, but what he didn't count on was being signed to the Keihin Athletics, the cheapest and worst team in the league. Can he help turn the Athletics around and (gasp) win the pennant? A gripping, edge-of-your-seat story loaded with Sakuishi's brand of wacky humor.
From Tokyopop: For the first 14 years of his life, Yukio Tanaka has been one heck of a boring guy. He has no hobbies, weak taste in music, and only a small vestige of a personality. He yearns for an exciting life, but his shy, and somewhat neurotic personality make him his own worst enemy. Little does he know that his life will be forever changed when he meets Ryusuke Minami, a wild and unpredictable 16-year old fresh from America, who happens to be in a rock-and-roll band named after his Frankenstein-like patched dog--Beck.