The Azulones host Los Rojiblancos at the Coliseum Alfonso Perez on Sunday, with Garcia Plaza expecting to face a team at the peak of their confidence.
"Atletico are proving they can compete with the very best," Football Espana quotes Garcia Plaza as saying.
"They had 13 straight wins in the League and in Europe. When a team does that they are an alternative to win the title."
However, Garcia Plaza believes that Simeone's men will be looking to bounce straight back with a victory to keep pace with La Liga leaders Barcelona.
"I don't give [their last two results] any importance," he added.
"We are talking of 13 wins in a row. That's crazy, and shows they're doing great with a talented coach and players who are very confident."
Atletico trail Barca by three points.