The conclusion of a three-year review by the international governing body of professional and junior tennis was that too few players are making a living from the game and that the age of those players is increasing.
Around 14,000 players currently compete in professional events, almost half of whom do not earn any prize money.
The ITF would like to reduce this to no more than 750 men and 750 women, and the central plank of the reforms, which have been approved by the ITF board, is for the introduction of a new Transition Tour from 2019.
The new tour would replace the lowest level of professional tournaments on the ITF Pro Circuit, with players earning ITF entry points instead of ATP or WTA ranking points.
The two systems will be linked to ensure that the more successful players are able to use their entry points to gain acceptance into higher-level tournaments.
The review found that, in 2013, only the top 336 men and 253 women were earning money once outgoings were taken into account, while the time taken to reach the top 100 had increased substantially.
Transition Tour events will be held within a localised circuit structure in an effort to reduce costs for both players and tournament organisers.
ITF president David Haggerty said: "The ITF's Player Pathway study is the most comprehensive review of professional tennis ever undertaken and has highlighted the considerable challenges at the base of our game.
"Over 14,000 players competed at professional level last year, which is simply too many. Radical changes are needed to address the issues of transition between the junior and professional game, playing affordability, and tournament cost.
"We have already taken an important step forward by increasing prize money levels at ITF Pro Circuit tournaments.
"The next step is to ensure the structure of professional tennis is fit for purpose through a targeted job opportunities approach that will create a smaller group of true professional players.
"We believe that the introduction of a new entry level to the professional pathway will allow players to take the first steps towards becoming a future champion within a more targeted and affordable circuit structure."
Read the original article on Eurosport: Tennis set for shake-up reducing number of professional players