Mainz have signed defender Fabian Schonheim from third-tier SV Wehen Wiesbaden on a contract until June 2014.
The former Kaiserslautern youngster had a year left on his deal at SV Wehen Wiesbaden and joins Mainz for an undisclosed fee.
SV Wehen Wiesbaden executive Wolfgang Graf regrets former Germany Under-21 international Schonheim's exit but realises his club could not stand in the 24-year-old's way.
Graf told Rhein Main Presse newspaper: "A player like Fabian Schonheim will not be easy to replace, however, we had to deal with reality.
"If there is a club from the top-flight it's very tough to compete for a club like us. It also would not have been fair to block Fabian Schonheim a return to the Bundesliga."
Mainz general manager Christian Heidel said: "We are happy to be able to add Fabian Schonheim to our squad for the new season.
"We have been watching him for some time and feel he can do a good job for Mainz in the Bundesliga."