The 19-year-old departed the Brazilian giants back in 2023 in a deal that was said to be in the region of £17.7m.
However, having initially contributed just two goals in 16 matches for Santos as a teenager, Washington has been provided with just 25 minutes of first-team football at Stamford Bridge across three appearances.
None of those outings have come under Enzo Maresca, the Italian recently reiterating that he had no plans to use the prospect as an alternative to the injured Nicolas Jackson and Marc Guiu.
Having just led Brazil to the Under-20 South American Championship, Washington has remained in his homeland to complete a return to his former club.
What are the details of Chelsea, Santos agreement?
When reports initially emerged, there appeared to be the possibility of Washington remaining at Estadio Urbano Caldeira until the end of June and then linking back up with Chelsea.
Instead, Santos have revealed that they have Washington's services for the remainder of 2025 and also possess the option to re-sign him on a permanent basis.
The potential fee in question has not been disclosed, but Chelsea are unlikely to have put themselves in a position to make a loss on the transfer at this stage when Washington possesses a contract until 2030.
Re-joining Santos at a time when boyhood idol Neymar has also moved back to the club is believed to have been a major factor in the deal.
Neymar has already gotten five appearances under his belt in the ongoing Campeonato Paulista, contributing one goal and one assist.
Santos are currently preparing for their first season back in the Brasileiro after securing promotion from the second tier in 2024.
Good deal for all concerned?
There will be those of a Chelsea persuasion that would have liked to see how Washington fared in the first team when Christopher Nkunku is struggling to make an impact as a number nine.
With a total of 10 goals and one assist from 18 appearances for the Under-21s, there have been glimmers of quality from the starlet.
Nevertheless, no-one can begrudge him for jumping at the chance of a return to familiar territory where he will hope to progress his career.
Scoring three times from seven games in the Under-20 South American Championship suggests that he could hit the ground running for his new side.
Written by
Darren Plant