The Colchoneros skipper believes his side dominated its game during their 2-0 loss to Almeria and has told his teammates to keep working.
The capital club had the chance to go back to the top of La Liga in Andalusia but slumped to its second defeat in a week thanks to two late Verza goals.
Gabi has admitted that his side was taken aback by the result but vowed to keep fighting for the club's first title since 1996.
"We did not expect this defeat," he is quoted as saying by AS. "We prepare in the best way possible to win matches and we dominated them, but they were more successful and a tricky game escaped us.
"It's unfortunate that the team have lost two games and we have to keep working."
Atleti suffered a 3-0 first-leg loss in the Copa del Rey against Real Madrid, but Gabi has vowed to fight in the second leg for a place in the final.
"We have to win the game. It's a very, very complicated semifinal, but we'll try."