Los Colchoneros were able to seal a narrow 1-0 victory thanks to Diego Costa's second-half strike, as they maintained pressure on Real Madrid, who overcame Malaga by the same scoreline earlier in the day.
Simeone acknowledged that Atleti were sluggish in the first half but expressed his delight with the reaction after the break and their will to win.
"The players are doing something extraordinary," the Argentine told a post-match press conference.
"I am speechless because they do their best to find results. I have admiration for this group of players.
"It was difficult because we were 1-0 up, not not for the lack of goal-scoring chances. Until you score the second though, the unrest remains.
"We handled it well, they had no great opportunities although they were able to attack. We were not accurate in the first half and we weren't fast enough, or playing between the lines."
Los Rojiblancos trail their cross-city rivals Madrid by three points in the league as they chase their first title since 1996 and Simeone insists that, despite their fatigue, they are driven by the desire of their supporters.
"We feel motivated when we see the shirt of Atletico," he continued.
"We identify with our fans. Everything costs a lot, everything is complicated and difficult, and we struggled, as does the vast majority of society."[The league] is hard for us because our rivals increasingly see possible game situations to beat us. The efforts we are making between Wednesday and Saturday, and Tuesday and Sunday [between Champions League and La Liga games] are huge."
Atleti sit second in the table with 67 points from 28 games, three behind leaders Real.