The team had its first training at the artificial turf of the Luzhniki Stadium on Friday, after which Kek said that the team had no injury concerns and that it will be at its best on match day.
"Everything about this match has already been said. It is clear that the Russian team is a big favourite. We are very happy to be in the play-offs," he added.
Russia's coach Guus Hiddink said that his team will be in attack mode on Saturday. "But we are not in a position in which we can expect an easy match," he added, rejecting suggestions that Russia was underrating Slovenia.
"All of us are aware that the match with Slovenia will not be easy. The stakes are too high," added the Dutch manager.
The return leg will be played in Maribor on Wednesday. The team scoring more goals on aggregate wins the play-off. If the scores are level on aggregate, away goals count double.
Should Slovenia eliminate Russia, it will qualify for the World Cup only for the second time in its history.
Slovenia has so far played three official games with Russia, with each team winning once and one match finishing in a draw.
