Professional tennis has several tiers, much like baseball with its major leagues and several levels of minor leagues below them. The best and most famous tennis players play in ATP or WTA tournaments. The rest, as many as 14,000 of them, toil anonymously around the globe in small events that are supposed to serve as tennis’s talent incubator.

Patrascu is one of those. Born in Bucharest, Romania, in 1997, she moved to Toronto with her parents when she was 5. She showed promise as a junior, winning the Canadian under-14 championship, and turned professional at 18. But her career-high ranking is No. 615 in the I.T.F. and No. 819 in the WTA.

Most players’ chances of making it to stardom are slim, and for many, it is challenging to just break even financially after paying for travel, training and other expenses. That is why the I.T.F., after commissioning an extensive study, declared the old structure unsustainable. Too many marginal players were basically masquerading as professionals.

The I.T.F.’s mission is to promote tennis around the world, and the organization works to ensure that there are tournaments on all continents. But those events have been open to all comers, and they have included players with little hope of breaking into the top tier — some of them over 50 years old. The I.T.F. study determined that in one year, as many as 6,000 so-called professional players did not earn even $1. A recent independent investigation also found that there was a “tsunami” of fixed matches at the lower levels, where players earning little prize money are vulnerable to betting syndicates.

The I.T.F. determined that the best model for professional tennis should include no more than 750 men and 750 women. It recommended new rules to restructure the tour, effectively eliminating almost 13,000 aspirants.