The Argentinean has overseen three wins and a draw from his first four games in charge of Los Rojiblancos since taking over from Gregorio Manzano.
More impressively, they have not conceded a goal in those games, but that record could come under threat when they face Unai Emery's third-placed side.
Despite being some 16 points off the pace in La Liga, Valencia are worthy of the spot they hold and gained an impressive draw with Barcelona in the Copa del Rey in midweek.
Typically, though, Simeone is refusing to credit not just his back line for the improvement, but the whole team.
Radamel Falcao has led from the front by scoring five goals in four games and goalkeeper Thibaut Courtois has barely had to make a save.
"When the defence allows a lot of goals the problem isn't about the defence, it's about the team," said Simeone, a former captain of the club, summing up the attitude he has employed since returning to Estadio Vicente Calderon.
"The best thing that has happened since my arrival is that the players have responded to the changes I have had to make."
Like Atletico, Valencia are in impressive form at the moment and are unbeaten in their last five games in all competitions, although their wins have been restricted to the cup only.
While they are hugely unlikely to haul back the 16 points between themselves and Real Madrid, they can strengthen their grip on a top-three berth by returning to winning ways in the league, with fourth-placed Levante five points behind them.