Inter Milan chief Piero Ausilio says AC Milan only signed Giacomo Bonaventura thanks to the Nerazzurri.
The Atalanta winger joined Milan last week.
"Inter had reserved two players and organised the situation for some time," director Ausilio told the Corriere dello Sport.
"The respective clubs were only waiting for Inter to call and offer the contract. When Guarin stayed, we advised the clubs involved, including Atalanta.
"Inter had reserved Bonaventura, but we released him and he became an opportunity for someone else. Perhaps until 20.30 on Monday Milan didn't even know the player was on the market."
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