Alguém falou em #JoãoMágico? 🤩
— Sporting Clube de Portugal (@Sporting_CP) October 6, 2020
The 27-year-old left Sporting for Inter four years ago with the Italian club paying €40m plus €5m in bonuses.
At first Mario was a regular in the Inter side, but fell down the pecking order under Luciano Spalletti.
That led to him joining West Ham on a half season loan in 2018, where he enjoyed a good spell.
Last summer he was loaned to Lokomotiv Moscow and again impressed, but the Russians could not finance a permanent deal.
Mario joined Sporting’s academy in 2004 when he was just 11 and wore the green and white shirt for over a decade.
He could not hide his delight at returning to the Estádio José Alvalade.
“The sensations are great,” said Mario in his first interview. “I always wanted to go back to where I feel good, where I was happy and where I want to be happy again.
“For me, it is a great honour to return to this house that I know well.”