The Ghana midfielder had started in Los Rojiblancos’ opening two league games against Getafe and Leganes. He started from the bench in this game, and it was the visitors that took charge in the opening 17 minutes, with Charles and Anaitz Arbilla giving them a 2-0 lead.
Atleti clawed one back via young sensation Joao Felix in the 27th minute before Vitolo made it 2-2 seven minutes into the second half.
Time was running out for Atletico in search of the winner and Simeone threw on Partey in place of Joao Felix in the 84th minute.
The golden moment would eventually come in the 90th minute through the Ghanaian midfielder as he linked up well with Saul Niguez, jinking past the Eibar defence, and slotting the ball home in fine fashion.
The result maintains Atletico Madrid’s perfect start to the season as they sit on top of the table with nine points after three games.
Partey has been an integral part of Simeone’s side, featuring in 42 competitive games last season, scoring three goals and providing six assists.
The 26-year old Ghanaian’s next league outing is an away trip to the Basque Country against Real Sociedad on September 14.