Fernando Morientes believes the Madrid derby is more important to Atletico, who risk falling too far behind their rivals and LaLiga leaders Real.
Real Madrid are two points clear at the top, but also six ahead of Diego Simeone's Atletico ahead of Saturday's clash at the Vicente Calderon.
Former Madrid and Spain forward Morientes feels that makes the encounter more crucial for Atletico.
"I think it's more important for Atleti," he said, via AS.
"The two play a lot, but Madrid have not lost yet... if Madrid win, the difference would be substantial."
Morientes also said the clash was an opportunity for coaches Zinedine Zidane and Simeone to be influential.
"It is the most important game of the season so far," the 40-year-old said.
"It will be a time to analyse the starting line-up and how they act during the match, the changes, how to modify the system."