Atleti gained 50 points from their opening 19 games of the campaign and share the Primera Division summit with Barcelona and Real Madrid, but the coach expects every team in the league to be tougher to beat as they set their sights on avoiding relegation or fighting for the title or a European spot.
Simeone told a press conference: "The second half of the season is always more difficult than the first because teams want to play attractive football at first and aren't just thinking about picking up points.
"But in the second half it's the opposite, everyone thinks about getting points and few think about playing, so it becomes more complicated. But we hope we can keep doing what we've been doing."
Simeone's side got their campaign off to a fine start back in August with a 3-1 win at Sevilla on the opening day of the season.
But the Andalusians head into the match at the Calderon unbeaten in their last seven games and aiming to close the six-point gap between themselves and Athletic Bilbao, who occupy the fourth Champions League spot.
Simeone highlighted the progress Unai Emery's side have made.
"Emery's work at Sevilla is paying off very well," he said.
"They've experienced many changes and are building a new team that are much more solid and practical.
"They have less possession but they are more direct and defend much better than before, and that's what makes them dangerous."
Simeone will be without holding midfielder Tiago Mendes, who is suffering from a muscle strain, meaning Koke will switch from his usual wide position into the middle.
Raul Garcia, who scored the second of the two goals against Valencia that saw Atleti qualify for the quarter-finals of the Copa del Rey in midweek, is also expected to start.
It remains to be seen if Garcia's inclusion will be at the expense of David Villa, who has not found the net in his last six games for Atletico.
Top scorer Diego Costa has also failed to score in 2014, but Simeone insisted he was not worried by either player's lack of goals.
"That's football and every player goes through a period when they either score goals for fun or struggle to score," said the coach.
"But both players are goalscorers who make the right movements and I'm sure they will get chances to score again. They just need to get the first goal and then others will follow in time."
Sevilla have a slightly larger absentee list than their opponents, with Diogo Figueiras suspended and Stephane M'Bia, Denis Cheryshev and Cicinho all injured.