The Frenchman was called in by coach Javier Aguirre after Leo Franco was forced to race to his wife's bedside for the birth of their baby.
In the Argentine's absence, Coupet saved Javier Portillo's spotkick to earn a point for Atletico and beamed afterwards: "I'm very happy for having stopped a penalty. It was important for the team and for me, because it reinforces the self-confidence, which is essential for any player. So I'm very happy.
"I stress that I am happy and now I need to work hard in training to continue performing well."