The 19-year-old had expected to join the Premier League new boys for the 2025-26 season, but circumstances have since changed.
He played just 103 minutes for Regis Le Bris' side, scoring his only goal in their 1-1 League Cup draw with Huddersfield Town, which they went on to lose on penalties.
Liam Delap’s reportedly serious hamstring injury, picked up in the 2-0 win over Fulham on Saturday, threw a spanner in the works for Chelsea.
Enzo Maresca’s side were initially intent on stopping Nicolas Jackson joining Bayern Munich on loan, but the Senegal international was adamant it would happen.
Chelsea have since secured a more favourable deal with the German club and decided to recall Guiu from his loan at Sunderland.
Jackson is now expected to join Bayern with an obligation to buy in the deal, if certain circumstances are met, rather than a simple option.