Brazil forward Vinícius Júnior has acknowledged that he and his teammates "can and must improve" after their frustrating start to the Copa América.

The Seleção were held to a goalless draw by Costa Rica in Monday's Group D opener in Los Angeles.

Brazil, who fielded an attacking line that included Real Madrid pair Vinícius and Rodrygo, had only three of their 19 shots hit the target.

"We know we can improve, we have to improve," Vinícius said. "I also know what I can improve, evolve and do for our team."

Brazil struggled against Costa Rica's five-man defence, much to coach Dorival Junior's exasperation as he eventually substituted Vinícius for Endrick in the 71st minute.

"We tried with him [Vinícius] on the wing and we didn't succeed," he said. "Then we put him inside and we couldn't find a way through either ... he was very well marked."

Dorival also brought on Sávio in place of Raphinha in the 71st minute, yet their struggles continued.

"We had to find a solution," he said. "I was trying to make a change. We tried various alternatives, several situations were created, but in the end we were unsuccessful with our finishing."

Brazil last won the tournament in 2019 and suffered a 1-0 home loss to Argentina in the final of the most recent edition two years later.

They have gone into the tournament, which is being held in the United States, in the midst of a disappointing South American World Cup qualifying campaign.

Brazil are sixth in the standings after winning only two of their six qualifiers and suffering three defeats, results that led to Dorival's appointment in January.

Despite being without their all-time leading scorer Neymar, who is recovering from injury, Brazil fans had high expectations after Vinícius' impressive season at Madrid.

He has asked Brazil fans to be patient.

"New coach, new players, everything takes time," Vinícius said. "Our fans want everything immediately done, but we're going little by little. In the next game, I'm sure we'll play much better because we now already understand what the competition will be like, what the pitch, what the referees will be like.

"Every time I enter the field for the national team, I have three or four players marking me."

On Friday, Brazil take on Paraguay, who lost 2-1 to Colombia on Monday. Neymar, who watched Monday's game from the stands at the SoFi stadium, is optimistic about his country's chances.

He wrote on Instagram: "There are days when we don't get anything right but there are days when you fit in. Being a football player means being judged all the time, with every pass, every shot, every choice.

"The game is over, we continue, let's train and get better for the next game. I trust this group a lot and I know that they will do the best they can for themselves, their family and all Brazilian fans!"