Jalen Rose weighs in on memo that Adam Silver sent to teams indicating that the "eligibility rules" for the draft may change by 2021. (2:08)

The NBA on Friday sent teams a memo indicating that "eligibility rules" for the draft may shift as early as 2021 (but no earlier) as the league reviews issues "related to player development and the corruption investigation in college basketball," according to a copy of the memo obtained by ESPN.

The memo does not mention the one-and-done rule by name, but it is meant to remind teams that the league and the players union could agree to scrap one-and-done before the expiration of the current collective bargaining deal in 2024 -- and perhaps well before then, sources say. The memo says that, as of now, the league does not expect changes in draft eligibility rules to take place at any time "prior to the 2021 or 2022 draft."

If such a change were to happen, it could create a single draft loaded with the best prospects from two consecutive high school classes.

The memo serves as something of an advisory to teams that might think about trading away future first-round picks in the lead-up to Thursday's draft. "As we approach the NBA Draft on June 21," the memo states, "and the increase in trade activity that often accompanies it, please be reminded of this ongoing review and the possibility that the eligibility rules could change" between 2021 and 2024.

As of now, no team owes a first-round pick in 2022 or any year beyond that. Three teams owe 2021 first-round picks, though two of those could change hands earlier under the protections assigned to them. (Memphis owes Boston a pick that is top-8 protected in 2019, top-6 protected in 2020 and unprotected in 2021. Milwaukee owes Phoenix a pick protected both 1-3 and 17-30 in 2019, top-7 protected in 2020, and then unprotected in 2021.) Only one unprotected 2021 pick has already been traded -- the pick Miami dealt to Phoenix in the 2015 Goran Dragic trade.

The league instituted the one-and-done rule in 2005, stipulating that players had to be either 19 or at least one year removed from their high school class graduation to be draft eligible.

In recent months, both NBA commissioner Adam Silver and Michele Roberts, executive director of the National Basketball Players Association, have spoken about the likelihood that the two sides might agree to end the rule. The league's current collective bargaining agreement runs through 2024, but the two sides are free to rework individual deal points between now and then.

Potentially allowing elite high school prospects back into the draft is just one part of the NBA's broader plan to revamp its relationship with youth basketball -- and specifically with players who wish to skip college and earn professional wages right away. The federal investigation into corruption within the youth and college basketball apparatus has created an opening for the NBA to extend its influence into those age groups.

The league had investigated the possibility of setting up European-style academies for the best U.S. prospects before shifting to other strategies. (The NBA operates academies in China, India, Senegal, Australia and Mexico.) League officials are still discussing ways to establish more points of contact with top high school players, including at camps and tournaments.

The league has long sought a true minor league system via its developmental G League. The G League will have 27 teams next season, with Portland, New Orleans and Denver the last NBA teams without G League affiliates. The NBA in April announced it will raise G League player salaries from a maximum of $26,000 per year to $35,000. The league last season introduced more lucrative two-way contracts for players who shuttle between the G League and the parent club.

A 30-team G League with competitive salaries would present prospects with a viable alternative to both college basketball and international leagues that do not operate with an age limit. The NBA has broached internally the idea of eventually adding a third round to the draft to give teams more chances at filling all these potential roster spots.

The league will discuss the issue further during annual meetings at Summer League in Las Vegas, the memo says.