Strasbourg have signed the 20-year-old on a permanent deal that includes a buyback clause for Chelsea, marking the 20th transfer between the two BlueCo-owned clubs since they came under the same American ownership group.
The move is expected to be the first of three deals between the clubs this week, with Chelsea striker Deivid Washington also set to join Strasbourg in a similar permanent arrangement, while either midfielder Dário Essugo or winger Mykhailo Mudryk could follow on loan.
Kellyman joined Chelsea from Aston Villa for £19million in 2024 but a series of hamstring injuries disrupted his time at Stamford Bridge, and he never made a first-team appearance for the club.
A successful loan at League One side Cardiff City last season, where he contributed to their promotion back to the Championship, restored his stock, and Strasbourg have moved to sign him permanently for a reported €6million — a steep discount on his original fee, though Chelsea's retained buyback clause means they can reclaim him at a fixed price if his development continues on its recent trajectory.
Elsewhere in Chelsea's crowded forward line, Emmanuel Emegha could yet leave the club before even making his debut. Reports in Italy suggest the 23-year-old, who is currently injured, is a target for Fiorentina, who are weighing up their options as former Everton forward Moise Kean edges closer to a move to Como. Should Kean depart Florence, Emegha would become a late-window alternative for the Serie A club.
Emegha was signed by Chelsea last summer but remained at sister club RC Strasbourg for the season before officially joining in July, and he is yet to make a debut in any form for the Blues, having missed every match of the summer tour in Australia and Hong Kong through injury.
He was not named on the bench for Monday's Premier League opener at Fulham, and is currently competing with Danny Welbeck for a spot behind João Pedro in Xabi Alonso's attacking plans — a battle in which Emegha appears to have already got the better of Nicolas Jackson for a place in the first-team group.
Both situations underline the scale of Chelsea's squad congestion as the transfer deadline approaches, with BlueCo's multi-club network continuing to serve as a release valve for players who have fallen down the pecking order at Stamford Bridge.
Chelsea currently have close to 40 senior professionals on their books, and further outgoing deals — whether to Strasbourg or elsewhere — are expected before the window closes on 1 September, with the club keen to trim numbers without losing long-term control of its most promising young assets.