Although Santos initially signed for the Blues 12 months ago, work permit issues meant that he was forced to wait before linking up with Chelsea in the summer.
While the Brazil international made an impression during pre-season, an array of midfield additions led to him being loaned out to Forest.
The hope had been that the 19-year-old would be given regular game in the Premier League before returning to Chelsea at the end of the season.
Instead, Santos has barely been used, predominantly by previous Forest boss Steve Cooper, with him initially being restricted to just one start in the EFL Cup second round against Burnley earlier in 2023-24.
Since then, the only time that Santos has made another first-team appearance is a brief cameo outing at Liverpool when Forest were already 3-0 down.
As a result, it has been an open secret that Chelsea would recall Santos and look to find him a different solution for the second half of the campaign.
On Wednesday afternoon, Chelsea confirmed that the formalities of exercising their break clause had gone through, the youngster now back at his parent club.
The West Londoners now have a decision to make regarding his next move given that their seven foreign loan slots are already taken up.
There is the possibility that one of Gabriel Slonina, Diego Moreira or David Datro Fofana could be recalled from their spells with Eupen, Lyon or Union Berlin.
However, a switch to another Premier League cannot be ruled out at this stage with Newcastle United said to be among those monitoring the situation.
Crystal Palace are another team that have been suggested as a potential destination as they bid to find an alternative to injured midfielder Cheick Doucoure.
Chelsea are unlikely to consider retaining Santos' services courtesy of him being cup-tied for the EFL Cup and there already being six players who are deemed to be ahead of him in the pecking order.