Xavi has told Barcelona to treat the Clasico against Real Madrid on Wednesday as a potential "turning point" as he prepares to hand Ferran Torres a debut.
The semi-final of the Supercopa de Espana takes place in Riyadh, Saudi Arabia, and comes in a season when Madrid have been lording it over their great rivals.
Madrid sit top of LaLiga, a distant 17 points clear of sixth-placed Barcelona, and Carlo Ancelotti's team are through to the knockout stages of the Champions League.
Barcelona must survive a nightmarishly difficult play-off against Napoli just to reach the last 16 of the Europa League, having flopped in the Champions League group stages.
Any trophy would be welcome at Camp Nou just now, and Barcelona could yet return from Saudi Arabia with silverware, with Xavi emphasising this opportunity to his players.
Barcelona have not beaten Madrid since a 1-0 league victory at Santiago Bernabeu in March 2019, and they will be up against it at King Fahd International Stadium as the teams battle for a place in Sunday's final.
Newly signed striker Torres and midfielder Pedri joined up with the squad on Tuesday after completing their COVID-19 isolation periods, reportedly travelling to Riyadh on a private jet along with president Joan Laporta.
Xavi said of the game: "It is a good opportunity to see where the team is at. It's a very important test for us. It could be a turning point.
"First, it gets you into the final, and then the confidence it gives to the project is tremendous. In two games you can win a title."
Injuries and coronavirus cases have meant Xavi has been short-handed at times, but he senses the core of a strong Barcelona is beginning to emerge.
Barcelona lost 2-1 at home to Madrid in LaLiga earlier this season, with that October defeat coming during Ronald Koeman's reign.
"We have to improve, we are building a project and it takes time, but tomorrow is a good test," said the Barcelona head coach.
"Pedri, Ansu Fati, Frenkie de Jong, Ronald Araujo ... tomorrow they will be important, and they will be in the future. I'm glad to have them back."
Xavi says Barcelona remain a team "under construction", with the former Barcelona midfielder adding this generation need to learn to "control games and kill games".
"Establishing this is not easy, but I am seeing positive things, and we need to grow," Xavi said. "We are Barca, and we have to reach the final.
"It is a Clasico, people are motivated to enjoy the competition and try to reach the final, which is the goal."
Former Manchester City striker Torres will feature at some stage, Xavi confirmed, providing the Spain international's registration goes through in time. Xavi said that was expected to occur soon.
These great giants of the Spanish game have been paired together at the semi-final stage because Madrid finished second in LaLiga last term, while Barcelona won the Copa del Rey.
Reigning LaLiga champions Atletico Madrid tackle cup runners-up Athletic Bilbao in the second semi-final on Thursday.
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