- Bats Right, Throws Right
- Height 6' 0", Weight 175 lb.
- High School Kusagabe Kyoei High School
Hiroyuki Kobayashi was drafted in the 4th round of the 1996 NPB draft by the Chiba Lotte Marines. Spending the next couple years in ni-gun, Kobayashi made his debut with Chiba Lotte in 1998, throwing 2 1/3 scoreless innings. He then was in ni-gun for another few years and did not pitch regularly for the Marines until 2001. At age 22/23 that year, Hiroyuki went 1-4 in 22 outings and had a 3.70 ERA. In 2002, Kobayashi went 7-4, 2.53 and struck out 84 in 81 2/3 innings over 58 games. He made his first Pacific League All-Star team that year.
In 2003, Kobayashi made 36 relief appearances and 14 starts and had a 10-10, 3.84 line. The next year, he was moved into the rotation full-time and went 9-7, 4.26. Named to his second All-Star squad, the right-hander struck out 137, third in the PL. 2005 was Hiroyuki's best year yet as he posted a 12-6, 3.30 pitching line, including a 5-0 record in six interleague starts as interleague play came to NPB. Kobayashi also hit .300/.333/.600 in interleague action. He got a 2 million yen bonus as he was named interleague play MVP. He finished 8th in the Pacific League in ERA, tied for 9th in wins and tied for 7th with 129 strikeouts. He won game three of the 2005 Japan Series, allowing one run in six innings. Additionally, he was chosen to play in the 2006 World Baseball Classic. In the classic, he pitched one game, getting lit up for three runs in one inning by Taiwan, though he struck out the side.
He was 10-7 with a 2.78 ERA in 2006, walking only 27 in 142 2/3 IP. He finished 6th in the PL in ERA, tied for 7th in wins and was 10th with 120 strikeouts.
Kobayashi retired all three batters he faced in the 2007 Asian Championship, striking out two.
A flashy player, Kobayashi is known for his fashion sense and once even experimented with cornrows. He has tried to stop ground balls from going past the mound by kicking them when out of reach. As a pitcher, he relies on a fastball (89-91 mph, peaking at 94), slider, forkball, and a changeup.