Borussia Monchengladbach have had a £14.25m bid for Andreas Christensen rejected by Chelsea, according to Sky in Germany.
The Bundesliga club are keen to bring the 20-year-old Denmark international defender to Germany on a permanent basis after he impressed during the first year of a two-year loan spell with them last season.
Christensen made 39 appearances for Monchengladbach in the 2015/16 campaign and scored three goals.
His loan will continue, although no further talks between the clubs over a permanent move are expected until the winter.
Christensen has made one Premier League appearance for Chelsea as a late substitute in their 3-1 win over Sunderland in May 2015 as well as starting two cup games earlier that season.
Meanwhile, Chelsea head coach Antonio Conte has has denied suggestions Diego Costa could be on his way back to Atletico Madrid, claiming the striker is happy to stay at Stamford Bridge.