Borussia Dortmund sign Chelsea's Ian Maatsen on loan to boost defence
The Dutch youth international made his Premier League debut last August and has made 12 appearances in the league this season.
"Because of our current squad situation we decided to act on the left back position this winter," Dortmund sports director Sebastian Kehl said. "Ian fits our profile with his strengths."
"He has a lot of pace, a strong left foot and can play various positions."
Last season's Bundesliga runners-up, Dortmund have struggled in the league and are currently in fifth place, 15 points behind leaders Bayer Leverkusen and six behind fourth-placed RB Leipzig, who occupy the last Champions League spot.
They have, however, advanced to the Champions League knockout stage where they face PSV Eindhoven - one of Maatsen's youth clubs - in the round of 16 next month.
The Bundesliga resumes later on Friday after a three-week winter break.
