Mainz land US youngster Jeffrey
The 19-year-old should officially link up with the Bundesliga club when the transfer window opens tomorrow and he will be given a long-term contract.
Mainz coach Thomas Tuchel told the German club's official website: "We are looking forward to him coming. He is a very talented player with a lot of potential. We are not setting him any limit and he will have the same chances to prove himself as any other player in the squad."
The midfielder has already begun training with Mainz and will fly with them to their winter training camp in Andalusia in the new year.