After coming off the bench and scoring in a penalty shootout win over Tottenham last week, former Bordeaux winger Malcom was named in the starting XI on Tuesday and proved to be a handful in Dallas, FourFourTwo magazine reported.
Facing the team who he rejected after Barca dramatically hijacked the deal at the last moment, Malcom was on target within four minutes of the second half at AT&T Stadium.
"He is a player that relates well with the game," Barca head coach Valverde told reporters.
"He is a strong player who can get between the lines and it is difficult to move him and he is a player who has a good shot.
"We are happy that this adaptation is quick."
Malcom was set to join Roma after the Serie A side reached an agreement with Bordeaux until Barca jumped in at the 11th hour.
Asked if signing the highly rated Brazilian winger was part of his plans, Valverde said, "The club works to have good players and that's what we're doing.
"I am a part of the club, the coach. But there are people who are dedicated to follow players and Malcom was a possibility. We are delighted with him because we see that he has many possibilities."