Mainz coach Kasper Hjulmand has been given a vote of confidence following a second cup elimination in just over a week.
Hamburg have signed Germany international Nicolai Muller after convincing Bundesliga rivals Mainz to sell.
Lyon and PSV Eindhoven were among the teams to claim wins in Thursday's Europa League third qualifying round first legs.
Mainz's general manager Christian Heidel says forward Nicolai Muller will not be leaving unless their demands are met.
Mainz have signed Chile international Gonzalo Jara on a two-year contract after he left Nottingham Forest.
Schalke have completed the signing of Cameroon striker Eric Maxim Choupo-Moting on a three-year deal from Mainz.
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