The Catalan giants made a bid for Atletico Madrid and Argentina striker Julian Alvarez, which was rejected.
"I have total confidence in (sporting director) Deco, we know that we have to do something," Flick told reporters after an inter-squad match at St. George's Park in England, where Barca have been training.
"It also depends (what happens) about Ferran (Torres)."
Spain international Torres, who scored the winning goal in their World Cup final triumph over Argentina, has one year left on his contract at Barcelona.
Torres has been linked with Champions League holders Paris Saint-Germain, coached by former Spain boss Luis Enrique.
Barcelona have signed Anthony Gordon and Karim Adeyemi this summer for the first team and Flick acknowledged both wingers could be used through the middle.
"Gordon and Adeyemi can play on both sides and as a number nine, so we have a lot of options actually," added Flick, who noted Spanish teenager Lamine Yamal was also capable of playing in that role.
