The Atletico Madrid star says that victory on Saturday will count for nothing if their form fades during the season and warns that they must not focus solely on Lionel Messi
Spain's top two head into their clash at the Vicente Calderon deadlocked on 49 points after 18 games.
However, Koke, who scored in Atleti's 1-0 league victory over Malaga, which briefly put Diego Simeone's side clear at the top, insists that nothing will be decided by Saturday's tantalising game.
"Whoever is top halfway through the season is incidental if you don't fulfill your objectives come the end of the season," he told reporters. "The second half of the season is going to be a long one. If we win on Saturday and then implode, it will mean nothing.
"I think we are very well prepared for the game. Of course, we've played some tough games recently, such as the one with Malaga, as well as Valencia, but [Barca] have also had to play during the week.
"Up to now we still haven't decided how we are going to approach the game because we've just had one recovery session [after the Copa del Rey match against Valencia].
"We played well in both Supercopa matches. To play well against Barcelona you have to work very hard, close them down, be tight at the back and be strong on the counterattack. We have to try as hard as possible to take the ball off them but we all know that it's difficult to do that against them."
Lionel Messi will by vying for a starting place after making an emphatic comeback from injury on Wednesday.
The Argentine ace came on as a substitute against Getafe in the Copa del Rey and scored a superb double, firmly putting him in contention for a start against Atletico, particularly with Neymar struggling with gastroenteritis.
"I don't know if Messi will play or not," Koke said. "If he does, we know he's the best player in the world. They have a number of the best players in the world in their team: Neymar, Messi and others."