Reigning champions and leaders Barca are eight points clear of second-placed Atleti, with just seven more matches of the league season to come after the crunch meeting at Camp Nou.
Diego Simeone's side, surprise Liga champions in 2013-14, continue to punch above their weight in competing with Barca and Real Madrid for major honours.
And Spain international Koke, while acknowledging the odds are stacked against his side, is determined to keep fighting for as long as possible.
"We will go with everything we have to win the game, it's our last bullet," the midfielder told beIN Sports .
"In the last few years we've been at a great level, we've always wanted to win but we have to be realists, there are huge teams in front of us."
Koke also hailed the importance of Antoine Griezmann, who remains the subject of speculation linking him with a move away from the Wanda Metropolitano.
"He's decisive for the team, even if he doesn't score," Koke said of his club's star man.
The midfielder also continued to praise team-mate Alvaro Morata, who he supported back in Feburary when the striker was struggling to find the net.
According to midfielder the January loan arrival from Chelsea has "given a boost to the team", although the striker is expected to miss the Barca clash due to a sprained ankle.
Barcelona's schedule is much more crowded and could do Atleti a favour down the stretch. The league leaders have at least 11 matches left in all competitions, including two crunch clashes against Manchester United in the Champions League.
Atletico sits five points clear of third placed Real Madrid as they look to keep their place among La Liga's elite.