According to Kevin O’Connor of The Ringer, the Wizards wanted two first round draft picks in exchange for Davis Bertans.
Washington's demand for Davis Bertans is two first-round picks, per league sources. Bertans will be an unrestricted free agent and the Wizards would like to re-sign him if they keep him. The Celtics one of multiple playoff teams with interest in acquiring Bertans.
— Kevin O'Connor (@KevinOConnorNBA) February 6, 2020
This essentially means that the team who acquires him will have to give up two future picks for essentially a half-season rental.