Traore joins the French side on a five-year deal, becoming the third Chelsea loanee to be sold so far this summer.
No More Waiting
The 21-year old had featured occasionally for Chelsea over the last few seasons and seemed to be closing in on a spot in the first team before being loaned out to Ajax last season. Scoring 13 goals in 39 games for Ajax, Traore helped guide them to the Europa League Final, beating his new club Lyon in the Semi Final.
Traore's Chelsea career had been littered with loan moves, which have helped his development, and the result is now a permanent move to one of France's biggest clubs. The deal is reported to involve clauses that would ensure Chelsea have an easier time in buying the player back if they choose to in the future.
The Burkina-Faso international now has the opportunity to focus on one club, rather than aiming to impress both Chelsea and the team that loans him. The move is a positive one for Traore's future and Chelsea will hope that selling him won't turn out to be a similar situation to Romelu Lukaku.
For now, Chelsea will let go of one of their brightest young stars in order to facilitate moves elsewhere. The day Traore returns to Chelsea could someday arrive as the Blues have shown in the past that they have a knack for buying back former players.
Chelsea have also let go of Juan Cudrado to Juventus, Christian Atsu to Newcastle United, Asmir Begovic to Bournemouth and Dominic Solanke to Liverpool this summer, while John Terry's contract at the club expires this summer.