Sergio Busquets has said it is "clear" that Barcelona need to make more signings following the departure of Neymar to Paris Saint-Germain.
Barca have signed Marlon Santos, Gerard Deulofeu, Nelson Semedo and Paulinho this summer but Busquets believes they still need to add to the squad, especially in attack.
Bids for Liverpool's Philippe Coutinho and Borussia Dortmund's Ousmane Dembele were rejected last week.
And Busquets told a news conference ahead of this week's Super Cup second leg against Real Madrid: "We need to improve each season.
"Obviously Neymar's position is where we've lost something. It's clear signings are needed. We have to strengthen the squad. We need attacking players to compensate for Neymar.
"But every position can be strengthened, and the more quality players that come in the better. I hope the best players arrive and that they generate competition and give the coach decisions to make."
Barca's weaknesses were exposed in Sunday's 3-1 first leg defeat to Madrid at Camp Nou, but Busquets said: "We know winning the trophy will be difficult but we are not giving up.
"We need to score three, but we've done that before at the Bernabeu so we will go out, try to be solid and get ourselves into a position to win the tie."
Coach Ernesto Valverde disputed the idea that Madrid had become the dominant team in Spain after their Champions League and La Liga double last season.
"I'm not going to say that," he said. "Maybe in moments, as they showed at certain times on Sunday when they took their chances.
"But does that mean they're better than us? No, I don't think that's a conclusion which should be drawn."
Valverde also stressed that Barca had not abandoned hope of winning the Super Cup, adding: "We won't throw the towel in. Past results are the inspiration to prove we can do it."
The Catalans will be without Andres Iniesta for the second leg, after the captain was substituted in the 68th minute of the first leg with a thigh injury.