The Blues are likely to have a very new defence after the summer transfer window.
Andreas Christensen and Antonio Rudiger are both leaving on free transfers when their contracts expire in the summer.
According to The Mirror, Bielefeld's Pieper is one of the players Chelsea are eyeing.
He is also out of contract when the season ends, which means Chelsea would not have to pay any transfer fee to bring him to the club.
The Blues were linked to Jules Kounde from Sevilla last summer and this winter, but it is unclear if they will go back in for him in the coming transfer window.
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