Atletico thumped Valencia, who are 18th in the standings with just five wins, 3-0 at the Metropolitano in September.
Atletico, meanwhile, are third with 50 points from 24 matches, just one point behind leaders Barcelona and second-placed Real Madrid.
"Those who saw Valencia play will interpret that they are different to those of months ago, they have more intensity, a correct tactical behaviour and at home they have a step more with their people (supporting them)," Simeone told reporters on Friday.
Simeone's side wasted a golden opportunity to go top in LaLiga after being held to a 1-1 draw at home by Celta Vigo on Saturday.
After two consecutive LaLiga draws, Atletico will look to return to winning ways against Valencia, who are on a three-match unbeaten run in the league.
"We've been fortunate enough to experience a lot of important games and we'll take it in our stride. Starting with a Valencia team that has improved with the new coach (Carlos Corberan), with a lot of order and that has made them grow," Simeone said.
The Argentine also backed Frenchman Antoine Griezmann.
The 33-year-old forward has scored 15 goals and provided six assists in 35 games across all competitions this season.
"He is an extraordinary player, differential, he makes us have a leap in quality. Of course, there are games where he doesn't do well, like so many other teammates. It will be up to me to interpret his game management. I have absolute confidence in him," Simeone said.