Complex Leagues are a minor league classification created with the 2021 Minor League Reorganization. Their legacy leagues were the Gulf Coast League and the Arizona League. A third circuit from the old Rookie Class, the Dominican Summer League, survived and its teams continue to be operated by their MLB parents under the branding. (The Venezuelan Summer League was decertified in 2015 due to ongoing political problems in the country). However, as a practical matter, the DSL is a step below the complex leagues . Typically, signed players not from the United States - who go through an entirely different signing process - start out in the DSL in the hope of graduating into a complex league and upward from there.
The level, formerly "Rookie", remains the lowest class of MLB's feeder system (unless the DSL is to be considered a one-league class), below what is now called Low-A. Two classifications comprising four leagues that previously lay in between - Class A-Short Season's New York-Pennsylvania League and Northwest League, and Rookie-Advanced's (Appalachian League and Pioneer League) - were eliminated. The GCL and AZL were renamed Florida Complex League and Arizona Complex League, respectively.
Players at this level are just beginning their professional careers and the leagues play shortened schedules. Because their parent teams' facilities - typically collocated with their spring training stadiums - have several diamonds each, these entry-level clubs' circuits came to be called complex-based leagues before that term showed up in their official names. Owned by their parents, they operate more like baseball camps than professional clubs – no admission charge, no concessions sales, rarely playing in the main stadium, with the parent sometimes even fielding more than one team.
The players are, however, pros – with opening-day service ranging from since the last amateur draft to up to three seasons, with the occasional more experienced player taking part while on a short-term rehabilitation assignment.