The semi-final of the Supercopa de Espana takes place in Riyadh, Saudi Arabia, and comes in a season when Madrid has been lording it over its great rival.
Kroos takes subtle swipe at Barca
Madrid sits atop LaLiga, a distant 17 points clear of sixth-placed Barcelona, and Carlo Ancelotti's team is 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, and Barcelona could yet return from Saudi Arabia with silverware, with Xavi emphasising this opportunity to his players.
Barcelona has not beaten Madrid since a 1-0 league victory at Santiago Bernabeu in March 2019, and it will be up against it at King Fahd International Stadium as the teams battle for a place in the final.
Newly signed striker Torres and midfielder Pedri joined up with the squad midweek 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," Xavi said. "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 remains a team "under construction", with the former Barcelona midfielder adding this generation needs 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 season, while Barcelona won the Copa del Rey.
Reigning LaLiga champion Atletico Madrid tackles cup runner-up Athletic Bilbao in the second semi-final on Friday (AEDT).