The Slovenians are looking for their first win in their third major tournament, having failed in Euro 2000 and the 2002 World Cup, and Kek conceded his players were nervous in what they see as a vital game.
"Tension and anxiety are creeping in but I think it's a good sign because it shows the players are operating like a team, unlike in the 2002 tournament when they were at loggerheads with each other," Kek told a news conference after Friday's practice.
"It is imperative to get off to a good start and while it would be unfair to talk about Algeria's weaknesses, I can say my staff and I have detected them and we are confident that we can chalk up three much needed points.
"Whatever happens in this World Cup I can guarantee that this crop of players will return home as a unit."
Kek promised in the build-up to the tournament his team would take risks to play entertaining football but striker Zlatko Dedic, whose goal in a 1-0 win over Russia sent Slovenia through to the finals, said the players had other ideas.
"Winning the opening game would open the door to the last 16 and we don't care how we do it, as far as I am concerned we can win all three group matches 1-0 with our goalkeeper Samir Handanovic being the only scorer," he said.
"We are fully focused on the opening match but we are also looking at the big picture in our group because reaching the knockout stage has to be our goal if we beat the Algerians."
Slovenia also play United States in Johannesburg on June 18 and England in Port Elizabeth five days later.
