Mainz are making an attempt to trump Chelsea for Japan international attacker Yoshinori Muto.
FC Tokyo announced last month they were in negotiations with Chelsea over Muto's sale.
However, Sponichi says the 22 year-old is reluctant to move to the Premier League champions, concerned his development will stall.
Instead, he favours moving to a smaller European club, with Mainz under consideration.
The Bundesliga outfit hope to beat Chelsea to Muto's signing with an offer of €5.5 million to FC Tokyo.