Atletico have fallen three points behind leaders Real Madrid after their draw in the Madrid derby last weekend and defeat to Osasuna.
Lopez knows Atletico have to get back to winning ways on Saturday to apply pressure on Real and Barcelona, who face Levante and Valladolid respectively this weekend.
"It's an important match because at this point, three points are like a final," the forward said.
"If we want to remain up (at the top) we need to win that match to take three points back home.
"We know the importance of Saturday's match. We are focused on it.
"Then we will face the (UEFA) Champions League match (with Milan), but now I just think the next match against Celta Vigo.
"The most important thing is to keep working and try to be good."
Atletico host Milan in the Champions League on Tuesday looking to book their place in the last eight after a 1-0 victory in the first leg.
