The 21-year-old goes into Sunday's La Liga match at home to Getafe on a high, having come off the bench to score the winner in his side's 2-1 victory over Hannover in the first leg of their Europa League quarter-final of Thursday night.
He has now scored five times in his last eight games, having previously netted just once all season, and he admitted the confidence his compatriot has shown in him has helped him to improve.
He told AS: "Luckily I have improved a lot lately. Since he arrived in Madrid, Simeone has given me a lot of confidence and this is important for a player. I am happier, I notice the belief he has in me when I go on to the field."
Despite his contribution on Thursday, Salvio is likely to start on the bench again with Arda Turan expected to keep his place.
Diego could make his first start in six weeks after returning from injury to make substitute appearances against Hannover and Real Zaragoza last weekend.
Getafe's run of 10 points from their last four games sees them travel across Madrid to the Vicente Calderon level on points with their neighbours and manager Luis Garcia believes they can make things difficult for Atletico after their European exertions in midweek.
He said to AS: "I don't know if the European game will affect them. Simeone will have it in mind, but they are eight points from the Champions League places and if we beat them then it makes even qualifying for the Europa League difficult so I think they will treat it as a final.
"They have very good players and a team worthy of playing in the Champions League, but we are level on points. They are favourites, but they will find a Getafe team doing very well."
Michel and Pedro Rios are suspended for the visitors and ex-Atletico man Juan Valera is injured, so Garcia is expected to draft in Miguel Torres at right-back, while Abdel Barrada and Francisco Casquero should return in midfield.