Borussia Dortmund defender Nico Schlotterbeck is reportedly refusing to extend his contract with the club due to disagreements with coach Niko Kovac. The German centre-back is said to be unhappy with the overly pragmatic and unattractive style of football implemented by Kovac. This situation has alerted several top clubs, with Bayern Munich and Liverpool both showing interest in securing his signature.Dortmund defender Schlotterbeck’s contract runs until 2027, but growing tensions with coach Kovac have cast uncertainty over his future, according to Bild. The German centre-back is reportedly unhappy with Kovac’s pragmatic and unattractive style of play, particularly following disappointing results against Bayern, Manchester City and Hamburg.Despite the friction, Dortmund are eager to keep Schlotterbeck at the club and are preparing a contract extension until 2030. The proposed deal would see his annual salary rise by around €2.5 million to at least €8m per year, with performance-related bonuses potentially taking the total package beyond €9m.Dortmund chief executive Lars Ricken expressed his support for Schlotterbeck’s decision to take his time before committing to a contract renewal. However, he also cautioned that the club would not wait indefinitely, saying: “We will not rush into anything. But of course, we don't want to drag it out indefinitely, everyone is aware of that.”Schlotterbeck joined Dortmund from Freiburg in 2022 and has since become one of the most important players in the squad. The German defender has made 134 appearances, scoring six goals and providing 14 assists. Known for his versatility, speed and strong one-on-one defending, Schlotterbeck has established himself as one of the top defenders in Europe. His ability to read the game and contribute to both defensive stability and attacking build-up has been crucial for Dortmund. He played a key role in the club’s 2022-23 Bundesliga title challenge, showcasing leadership and consistency throughout the season. Schlotterbeck refused to commit his future to Borussia Dortmund after their 2-1 defeat to Bayern, saying: “I still have over a year and a half left on my contract. I'll sit down with Sebastian [Kehl], work out a plan, and see where it leads.” While the defender insisted that he is happy at the club, he acknowledged the significance of the decision regarding his contract renewal, stating: “I feel very comfortable in Dortmund and have no problem continuing on this path. But it's obviously an important decision for my career.”Looking for smarter football bets? Get expert previews, data-driven predictions & winning insights with GOAL Tips on Telegram. Join our growing community now!Bayern have shortlisted Schlotterbeck as a potential replacement if Dayot Upamecano leaves the club on a free transfer, viewing the Dortmund defender as an ideal long-term option. Germany’s World Cup-winning captain Lothar Matthaus has made his stance clear, stating that Bayern cannot afford to hesitate. He believes that Schlotterbeck should be seen as more than just an alternative, describing him instead as the logical successor should Upamecano leave the club. “If things don't work out with Upamecano, then Schlotterbeck would definitely be more than an alternative," he said. "Then bringing him to Munich would almost be a must.”Matthaus believes Schlotterbeck’s experience in the Bundesliga would be a major advantage, saying, “Because he’s familiar with the Bundesliga, because he plays alongside [Jonathan] Tah in the national team.”Meanwhile, Spanish giants Real Madrid are also monitoring the defender as a potential target if their pursuit of Upamecano fails. Schlotterbeck is viewed as a reliable long-term partner for Dean Huijsen, with Antonio Rudiger and David Alaba nearing the later stages of their careers and Eder Militao struggling with recurring injuries.Premier League side Liverpool have also shown interest, identifying Schlotterbeck as a possible replacement for the injured Gabriele Leoni, with Ibrahima Konate’s contract set to expire soon.Dortmund will aim to gain clarity on Schlotterbeck’s future by the end of the season, as his continued refusal to extend would leave the club with only a year left on his contract, significantly reducing his market value. Bayern could be in pole position to sign him, although their interest may cool if Upamecano agrees to a contract extension.For now, Dortmund and coach Kovac will use the international break to analyse their recent defeats and implement necessary tactical adjustments. Meanwhile, Schlotterbeck remains focused on finishing the season strongly before evaluating his options in the summer.