Silva, 22, joined Milan last season for a reported €38m fee from FC Porto with a fearsome reputation, due to his prolific record with Portugal and FC Porto.
However, the striker who's netted 13 times in 28 caps for his country, that Ronaldo dubbed as his successor, scored a paltry two Serie A goals in 24 games during the 2017/18 campaign.
This led to his off-season loan to Sevilla, where he now leads the scoring charts, with seven goals in as many games, ahead of the likes of Lionel Messi and Luis Suarez.
"He didn't want to stay," Gattuso told reporters after the Sassuolo victory. "He wanted to leave at all costs.
"He's scoring goals now and we did everything possible to persuade him to stay but he wanted to go, like [Carlos] Bacca when he went to Villarreal.
"I know that André is proving decisive at Sevilla but it was him that decided to leave. Nobody kicked him out."