According to Spanish media outlet Mundo Deportivo, Barcelona are interested in a January move for Chelsea defender Antonio Rudiger following the injury to Gerard Pique.
Pique is set to miss four to six months of football after suffering an injury last month, making it crucial that Koeman brings in defensive reinforcements.
The arrival of Thiago Silva at Chelsea this season has pushed Rudiger down the pecking order at the club, with Chelsea boss Frank Lampard preferring Silva and Kurt Zouma as his first choice centre-back pairing.
The report claims Chelsea are willing to let Rudiger join Chelsea in January, with football stats site Transfermarkt valuing the centre-back at £27million.
Chelsea currently have five centre-backs at the moment and Lampard is reportedly open to letting one of Rudiger, Fikayo Tomori or Andreas Christensen leave in January.
Rudiger is contracted at Stamford Bridge until July 2022.