Newcastle United are reportedly monitoring Kacper Potulski, an 18-year-old central defender for Mainz 05 who recently changed his agent. A departure from his current club is not being ruled out, and Bayer Leverkusen also remains an interested party. Borussia Dortmund had considered the Polish defender, but he was viewed as an alternative before they moved to sign another target. Potulski has a contract with Mainz until June 2028 and has two caps and one goal for Poland. His current market value is listed by Transfermarkt as €18.00m. In the 2025/2026 Bundesliga season, he made 15 appearances, scoring one goal and providing one assist.