Wirtz, one of the best German talents of this generation, was essential to Bayer Leverkusen's undefeated march to the Bundesliga title last season. The 21-year-old is drawing interest from numerous elite clubs throughout Europe as he develops and is perceived as one of Germany's future great products. As per German publication BILD, Leverkusen may struggle to hold onto Wirtz beyond this season and there are four clubs in the running to sign him next season.