The defending champions won 2-0 at home over Real Sociedad on Tuesday for their third straight league victory and to remain in third place.
“I think the battle for third place is going to be very complicated,” Simeone told his club’s official website. “Sevilla are winning and are playing well.
“Valencia now have the responsibility to win in Bilbao. “
Atletico are four points clear of Valencia, who play at Athletic Bilbao on Thursday.
Sevilla are level on 61 points with Valencia in fifth place after their 2-1 triumph at Levante on Tuesday.
“Each game from now on is a final and my prediction is that third spot will not be decided until the end,” Simeone said.
The top three teams in La Liga qualify directly for Champions League football next season.
French forward Antoine Griezmann, who scored his 16th league goal against his former club to help Atletico to victory, said: “We are up there fighting for the Champions League and we have to continue like this.
“Yes, we have to be strong.”
Atletico have kept a clean sheet in their last four league games and play at Malaga on Saturday.
“We know that if we keep a clean sheet, it is easier to win, we have to continue like this,” Griezmann said.