The Germany U21 defender has impressed in his first year in Italy.
Baccin told Sky Italia: "He was on a short list that we identified, we started to follow them, even at the Under 21 European Championship.
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"After an internal discussion we went straight to him, we are very happy, he was a player within the parameters we had thought of.
"I must say that his impact with our environment was incredible, he entered with a mentality and intelligence that impressed us."