The move is a return to the Bundesliga for the Ghanaian left-back who signed for Chelsea from Augsburg a year ago.

Last season he made 23 appearances, 19 of them starts, with his debut also his first career game in the Champions League, a 4-0 win over Maccabi Tel Aviv.

Schalke finished fifth in the German top flight last season and have former Chelsea striker Franco Di Santo in their squad. Baba will reunite with his former Augsburg manager Markus Weinzierl who took charge of Schalke earlier this summer.