The hosts have yet to concede a goal in the tournament, including when they thrashed Peru 5-0 in a group-stage match earlier in the competition.
And keeping their goal intact will be key to lifting a ninth Copa crown, according to the Real Madrid man.
"Ending the competition without conceding a goal is one of our aims," said Casemiro.
"And if we don't concede a goal, it's not just thanks to the guys at the back, those up front help us a lot and that makes the difference."
The woodwork also made a difference in Brazil's 2-0 semi-final victory over arch rivals Argentina, as did referee Roddy Zambrano's refusal to consult VAR twice when Lionel Messi and his team-mates were claiming a penalty.
Sergio Aguero headed against the bar in the first half and Messi rattled the post after the break, while Brazil captain Dani Alves and midfielder Arthur both got away with blatant off-the-ball fouls inside the area on Manchester City pair Aguero and Nicolas Otamendi respectively.
Argentina have complained to South American football's governing body CONMEBOL over the refereeing in that semi-final, although to no avail as the result will not be changed.
Brazil have identified the main threat to their defensive invincibility on Sunday at Rio de Janeiro's iconic Maracana stadium: Peru forward Paolo Guerrero.
He's a player well known to Brazilian fans having spent the last seven years playing in the country.
The 35-year-old scored the winning goal for Corinthians in the 2012 FIFA Club World Cup final against Chelsea.
Currently playing for Internacional in Porto Alegre, he previously helped Corinthians win the Sao Paulo state championship in 2013 and Flamengo to do likewise in the Rio state championship four years later.
"He's a player who deserves special attention for everything he's done in the past," said center-back Marquinhos.
"I know him well, I played with him for a bit at Corinthians and I've played against him several times for the national team."
One of those was two weeks ago at the Corinthians Arena in Sao Paulo when Guerrero was kept quiet while Peru when into a defensive meltdown.
They've bounced back spectacularly from that set-back, though, first ousting Uruguay on penalties in the quarter-final, in a match in which they were clearly second best, and then in a stunning performance to beat the outgoing champions Chile 3-0 in the last four.
"It'll be a great final, a really difficult match. We can't think it's already won, we have to play it," said Casemiro.
"They've eliminated great teams -- Uruguay and Chile -- we have to respect them."
It's only the second time Peru have reached the Copa final in its 103-year history.
They beat Colombia in a play-off in Caracas in 1975 after each side had won at home in a two-legged title decider.
And their first title in 1939 on home soil came at the end of a single five-team tournament played in a round-robin format.
"We've got to approach it calmly. It's true that we've achieved something very important after many years," said forward Raul Ruidiaz.
"We're aware and calm that there's one more step to glory.
"We need to play with our feet on the ground and give everything on the pitch to make it happen."
Brazil, in stark comparison, have won the Copa eight times and finished runners-up on a further 11 occasions, a record bettered only by Uruguay and Argentina.
From 1997 to 2007, Brazil won four out of five editions of the Copa, missing out only in 2001 when the Selecao turned up in Colombia without leading lights such as Ronaldo, Rivaldo, Ronaldinho and Roberto Carlos -- four crucial players in their World Cup success the next year.