Developmental player system (Nippon Professional Baseball)

Updated 2026-10-03

Developmental player system (Japanese: 育成選手制度, Ikusei Senshu Seido), also rendered as the Developmental Player System, is a player-contract framework in Nippon Professional Baseball (NPB) established in the fall of 2005. It allows NPB clubs to sign and retain players for training purposes outside the 70-man limit of "registered players under control" (支配下選手, shihai-ka senshu). The system has been compared to practice squads used in other sports.

On English Wikipedia, "Developmental player system (Nippon Professional Baseball)" is a redirect to the article "Developmental Player System"; the concept is also documented in Japanese-language encyclopedic and official sources, including NPB's own "Regulations Concerning Developmental Players of Nippon Professional Baseball" (日本プロ野球育成選手に関する規約).

Terminology

Developmental player (育成選手, ikusei senshu): a player under a developmental contract (育成選手契約 / 育成契約).
Registered player under control (支配下選手, shihai-ka senshu): a player on the ordinary roster, eligible for first-team (一軍) official games; each club may register up to 70 such players.
Movement between the two categories is commonly described as "promotion to control" (支配下昇格) and "demotion to developmental" (育成降格 / 育成落ち).

Background and establishment

The system was introduced in 2005, in a period when corporate (company-sponsored) amateur baseball teams in Japan were being disbanded amid prolonged economic stagnation, reducing opportunities for amateur players to gain experience. Its stated purpose was to create an environment in which such players could continue training and playing within professional organizations. Players in the system are sometimes described as "semi-controlled": they play for the club that signs them, but the club does not hold the exclusive rights that apply to controlled players.

Prehistory

Before the system, players exceeding the then-60-man controlled roster limit were sometimes handled as rinshūsei (練習生, "practice players"), who could train with a team but could not appear in official first- or second-team games. A 1970 agreement prohibited clubs from hiring undrafted players as practice players or club employees, but it was widely circumvented; clubs were accused of using the practice-player arrangement to "lock up" draft prospects. Documented cases include Isao Itō, Taihō Yasutaka, and Shin Nakagomi. In the late 1970s the Crown Lighter Lions (now the Saitama Seibu Lions) also recruited junior-high graduates as practice players in a development program. Proposals to abolish the roster cap at that time were not adopted.

Principal regulations

Details are governed by NPB's developmental-player regulations, which differ from the main Japanese Professional Baseball Agreement (野球協約).

Player rules

Developmental players may not appear in NPB first-team official games. They may appear in the minor leagues (Eastern League and Western League) subject to a per-game limit per team (originally five players per game). Participation in some other competitions, such as spring/autumn educational leagues, the Fresh All-Star Game, and the Farm Japan Championship, has been permitted since the late 2000s. Because of the per-game limits, some clubs have formed third or fourth squads to play games against independent-league, corporate, or university teams.
Contracts run for a maximum of three years. After that period, a player may become a free agent once and may re-sign with the same club on one-year extensions; if not signed to a controlled contract, players become free agents automatically or are placed on the developmental-player retention list (育成選手保留者名簿).
The minimum annual salary is ¥2.4 million, with a ¥3 million preparation payment (支度金) upon being drafted. There is no cap on salary, and players converted from controlled contracts often retain controlled-level pay.
Developmental players wear three-digit uniform numbers (e.g., 001, 101, 201), while other players and staff use one- or two-digit numbers. Clubs often derive the three-digit number from a player's former controlled number (for example, 24 → 124).

Team rules

A club may hold developmental players only if it has at least 65 controlled players on its roster as of July 31 (with provision for clubs to report and obtain approval in certain cases).
There is no fixed limit on the number of developmental players a club may hold. Practice varies widely: the Yomiuri Giants and Fukuoka SoftBank Hawks have at times held more than 30, while the Hanshin Tigers have typically held few. Fukuoka SoftBank has used the system to support a four-team structure.
The window for converting a developmental player to a controlled contract runs from the end of the season to July 31 of the following season. Since the 2008 season, clubs may not move a player from a controlled to a developmental contract during the season, though off-season re-signing is permitted.
Under Article 11 of the regulations, trades of developmental players concluded by July 31 are allowed. At least through the early 2020s, such trades were rare.
A provisional rule change reported for June 1, 2026, would conditionally raise the per-game minor-league limit from five to seven developmental players, in connection with the use of a 10-day injured list for controlled players.

Developmental draft

New players are acquired through a Developmental Players Selection Meeting (育成選手選択会議, commonly called the 育成ドラフト or "second draft"), normally held after the regular NPB draft. It is convened with the participation of interested clubs if the total number of players selected in the rookie draft has not reached 120. Selections count toward that 120-player framework. The procedure does not apply in the same way to players who have previously held controlled contracts or to foreign players.

A related registration category, trainees (研修生, kenshūsei), also exists within the system, with distinct rules allowing acquisition without the draft; as of the most recent available data, no player has been registered as a trainee.

Outcomes

The system began in the 2005 season. On May 23, 2006, Yusuke Kosai and Michitaka Nishiyama of the Fukuoka SoftBank Hawks became the first developmental players promoted to controlled contracts; Nishiyama made his first-team debut on May 28, 2006, and Kosai recorded the first hit by a developmental-origin player in 2007 and the first home run in 2008. Tetsuya Yamaguchi of the Yomiuri Giants became the first developmental-origin player to win the Rookie of the Year Award (2009), the first to win a major seasonal title, and the first to reach an annual salary of ¥100 million.

Subsequent developmental-origin players to achieve prominence include Kodai Senga (later of the Fukuoka SoftBank Hawks and the New York Mets), Takuya Kai, Shuta Ishikawa, Ukyo Shuto, Yoshifumi Okada, Tetsuya Matsumoto, and the foreign players Liván Moinelo, Raidel Martínez, and Yariel Rodríguez. The Yomiuri Giants and Fukuoka SoftBank Hawks have promoted large numbers of developmental players to controlled contracts.

The number of developmental players selected in the draft has trended upward since the late 2000s, with record numbers reported in the 2020s (reports for the 2022 draft give figures of 51 to 57 selections depending on the source).

Criticism and controversies

Use for purposes other than development. The system has been used for injury rehabilitation (for example, after Tommy John surgery), for evaluating players released by other clubs, for temporary roster reinforcement, and to allow veteran players to appear in ceremonial retirement games without consuming a controlled roster spot. Such uses have been criticized as contrary to the original intent of developing amateur players, and as an alternative to systems such as Major League Baseball's injured list.
The Kanemoto Akihiro case (2007). The Chunichi Dragons attempted to place a second-year player, Akihiro Kanemoto, on waivers and re-sign him as a developmental player in order to free a controlled roster slot. The players' association objected that this risked turning the system into a loophole for roster reinforcement; the Central League ordered the waiver withdrawn, and Chunichi's subsequent re-application was rejected. The club ultimately released Kanemoto, who declined a developmental re-signing and retired.
Relations with independent leagues. From 2012, NPB approved the dispatch ("loan") of developmental players to independent leagues (Shikoku Island League Plus and Baseball Challenge League); from 2024, dispatch to the farm-participating clubs Oisix Niigata Albirex Baseball Club and Hayate Ventures Shizuoka was also permitted.
Corporate amateur players. The Japan Baseball Federation has generally opposed selecting players from corporate teams in the developmental draft, arguing that such players fall outside the system's stated educational rationale, though no explicit prohibition exists.
Per-game participation limits. The restriction on the number of developmental players who may appear in minor-league games has been criticized by managers and others as excessively restrictive, prompting the provisional 2026 revision noted above.

Records

Oldest developmental contract. Japanese-language sources describe Noriaki Iwase (Chunichi Dragons, 2018) as the oldest player to sign a developmental contract. English-language sources cite Soichi Fujita, who signed in 2011 at age 39. Reported records differ by source.
Longest service. Kousuke Naruse spent eight seasons (2011–2018) as a developmental player, the longest such period as of the 2022 season.