Mainz general manager Christian Heidel says it will take a substantial bid for the club to consider any offer for striker Adam Szalai.
The 25-year old found the net 13 times in his 29 Bundesliga appearances last season, bringing him to the attention of a number of clubs.
Szalai has two years remaining on his current contract and Heidel says that he plans to keep hold of the Hungarian.
"Adam Szalai has an ongoing deal at our club and we don't plan to let him go," he told BILD.
"Of course, if someone intends to fill us up with money, we would start considering this. To see Adam leave we would need to cash in big money."
Bundesliga rivals Stuttgart were one of the clubs rumoured to be chasing Szalai but general manager Fredi Bobic was quick to dismiss the suggestion.
"Adam Szalai is a player of FSV Mainz 05 and I really wonder as I don't know where this gossip might come from," Bobic also told BILD.