Joao Felix joined Atletico for €126million in pre-season, coming in as the replacement for Antoine Griezmann after his move to Barcelona.
The 19-year-old attacker impressed in the close-season, particularly when getting a goal and two assists in the remarkable 7-3 friendly win over rivals Real Madrid in July.
He has had a slightly slower start to life in competitive action for Atletico, scoring twice and setting up one goal in seven LaLiga outings, but Simeone was impressed with his display in Moscow.
The Portugal international scored Atletico's first goal from close range after chasing up his own effort that rebounded back off the goalkeeper, before then playing a key role in their second – winning the ball back and picking out Diego Costa, who squared to Thomas Partey for the finish.
"It was the match in which he was most involved, possibly, in the rhythm of the game," Simeone told reporters ahead of Sunday's trip to Real Valladolid.
"For a player who likes to have the ball, participate in the game of his team, it [the performance] generates more enthusiasm.
"The other day this happened, he was active in the two goals of the team. That will lead him to continue growing.
"What I liked most was when he threw himself on the floor and retrieved a ball near the bench and showing that he understands what football is."
Simeone has been rotating his options in attack this season, opting to play all three of Joao Felix, Costa and Alvaro Morata on Tuesday.
And, according to the coach, that is advantage Joao Felix brings; he can feature either out wide or in a support role behind two main strikers.
"Due to his characteristics, he can play accompanied by a striker or with two striker references," Simeone said. "He has a great vision of the game and the team has more possibilities playing with two strikers and plus Joao, but the work balance of the rest of the team rises and will depend on the players.
"I think he can play in both versions. When he arrived I think he came with chances to play as a second striker. Now, when he participates most is with Costa and Morata, he has more vision to participate."