The potential movement of players to both EuroLeague and EuroCup rosters is coming up on some deadlines. Here's what you need to know.
How do EuroLeague mid-season roster moves work?

The rumor mill is in full swing these days, with lots of Turkish Airlines EuroLeague players being linked with mid-season moves to other clubs inside the competition.
If and when those changes happen, the timing of each will influence when fans can see a new player suit up in their team's uniform to help in the playoffs push.
In short, if such a move happens in 2023, fans will have to wait until 2024. But if it happens between New Year's Eve and the roster cutoff date in early February, then they can see their team's new player as soon as the paperwork goes through.
Three players are already waiting to return to action after changing EuroLeague clubs recently, and more may soon find themselves in the same situation.
Back on November 21, Olympiacos Piraeus signed Naz Mitrou-Long away from Zalgiris Kaunas by paying his buyout clause. Nonetheless, Mitrou-Long remains ineligible to suit up for the Reds in EuroLeague games until Round 18 due to a bylaw that prohibits any player appearing for two different teams in either half of the regular season. That same bylaw applies to new Crvena Zvezda Meridianbet Belgrade recruit Freddie Gillespie, signed away from FC Bayern early this week, and to Shabazz Napier, who returned to EA7 Emporio Armani Milan on Thursday from Zvezda.
How EuroLeague-to-EuroLeague transfers work
Players moving from one EuroLeague club to another may be registered to play only between the end of Round 17 and the eve of Round 26.
This season, that means between December 30 and February 7. In all cases, a player must be deregistered by their old EuroLeague club before he can be registered with another one.
For signings of players who come from other leagues, such as the NBA, the deadline is also 18:00 CET on that Wednesday, February 7, but they may be signed, registered and begin to play at any time before that.
Bear in mind that no team may register more than 20 players in a season or more than 16 at any one time. Those limits, however, do not include players who were born January 1, 2004, or later. Therefore, most teams have ample space to add players if they so choose before the February 7 deadline.

What about EuroCup-to-EuroLeague signings?
For EuroCup-to-EuroLeague signings, again, the Round 26 deadline in the EuroLeague applies. As such, a player currently playing in the EuroCup will be able to join a EuroLeague club at any time before the February 7 deadline.
At the same time, however, EuroCup players are no longer able to join other EuroCup teams because the halfway point of that competition's regular season has passed. The only exception to that would be if a player had been deregistered from a EuroCup team before Round 9 of the 18-game group stage, in which case they would still be able to join another EuroCup team until 18:00 CET on Tuesday, January 9, just before the start of Round 14. That is also the date on which EuroCup rosters are closed for the season, so any new additions from outside the competition must be completed by then.