By ESPNSTAR.com staff
Goals from Diego Costa and Emre Belozoglu were enough to hand the La Liga outfit three points against their Portuguese opponents, who netted a late consolation through Salim Cisse, which kept up their 100% record in the competition this season.
Atletico have also been impressive on domestic soil since the start of the campaign and are currently second in the league, behind Barcelona only on goal difference, but Simeone has warned his players not to get ahead of themselves.
"The result sets us up nicely," he said in his post-match press conference. "Now we can work quietly and calmly but we have to keep winning.
"In the second half, we had more aggression and intensity about our play. The result should have been 3-1."
The Rojiblancos now turn their attention to the weekend's La Liga game against Osasuna, a team Simeone expects will pose a real test.
"We will prepare well for Sunday as we have a very tough opponent in the form of Osasuna," the ex-Argentina international added.
"God permitting, hopefully those who have played today [Thursday] will recover in time."
One of Atletico's stars of the season has been Radamel Falcao, who has already netted nine times in the league in just eight games.