Borussia Dortmund do not have first option on Ian Maatsen this summer, with Chelsea's £35million release clause open to any clubs interested in the 22-year-old left back.
Maatsen enjoyed an excellent loan in Germany, though endured an unfortunate end to the season in Saturday's Champions League final, playing the erroneous pass which saw Real Madrid score their second goal at Wembley Stadium.
Maatsen had impressed before that mistake and Dortmund, more than pleased with his overall work, want to keep him.
They are the favourites to secure a permanent transfer, but could yet face competition for the Chelsea loanee, who has been monitored by clubs in the Premier League and La Liga.