The 23-year-old is approaching full fitness after nearly 11 months out with an anterior cruciate ligament injury which he picked up playing for Ghana against Uganda in the Africa Cup of Nations.
Rahman, a £14million signing from Augsburg in 2015, was sent on loan to Schalke last season and the Bundesliga side are keen to take him again in January.
However, they are not alone. Everton want cover for Leighton Baines and are weighing up a number of options while Monaco, Fenerbahce and Fiorentina are also keen to take him.
Rahman has been training with Chelsea's first team but Antonio Conte is still keen on adding another left-sided wing-back with Porto's Alex Telles and Alex Sandro of Juventus on his wishlist.
Rahman has made 23 appearances for Chelsea, but none at all since the final day of the 2015-16 league season.