Borussia Dortmund have made a significant move in the transfer market, submitting a concrete €20 million offer for Mainz 05’s highly-rated young centre-back Kacper Potulski.
According to reports circulating in Germany, the Bundesliga side are keen to strengthen their defensive options with the 18-year-old talent, who has recently earned a senior call-up for Poland.
Mainz, however, have turned down the proposal, insisting on a higher fee for one of their most promising defensive prospects.
Potulski has impressed this season, making 15 Bundesliga appearances during the 2025-26 campaign. He contributed a goal and an assist, showcasing both defensive solidity and attacking threat from the back.
The young defender joined Mainz from Legia Warsaw’s youth academy in the summer of 2023 and is currently tied to the club until 2028.
His contract does not contain a release clause, giving Mainz strong negotiating power as interest in their player continues to grow.
Bayer Leverkusen are also understood to be monitoring the situation closely, potentially setting up a competitive bidding process.
Potulski’s rapid rise has drawn attention across European football. Known for his composure on the ball, strong aerial ability, and tactical awareness, he represents the new generation of Polish defensive talent.
His international call-up further highlights his growing reputation and potential to develop into a top-level performer.
In preparation for the upcoming season, Borussia Dortmund have already moved to bolster their backline.
The club recently completed the signing of 19-year-old Joane Gadou from RB Salzburg in a deal reportedly worth around €20 million.
This acquisition suggests BVB are actively investing in youthful, high-potential defenders as they look to build a more robust squad capable of challenging for silverware both domestically and in Europe.
The pursuit of Potulski reflects Dortmund’s strategy of targeting emerging stars before their value skyrockets. With Mainz holding firm on their valuation, negotiations could extend into the coming weeks.
Should Dortmund meet the asking price, Potulski could become a key figure in their defensive rotation for years to come.
