Speculation of his imminent firing has been rampant in Spain since Madrid went on a five-game winless streak that included its longest ever scoring drought.
An unconvincing 2-1 win over Viktoria Plzen this week did little to change the mood that Lopetegui is in serious danger of losing his job.
Lopetegui said on Saturday he still hopes to turn around Madrid's season a day before his team visits Barcelona's Camp Nou.
When pressed about his future after the match, he said: "I hope I am still breathing, I don't think I am going to die. Our situation is not irreversible, we are in October."
Madrid has fallen to eighth place after back-to-back Spanish league losses against Alaves and Levante. Even so, it is only five points behind new leader Atletico Madrid, which won on Saturday.
Blasted in the Spanish media, Lopetegui has so far maintained the public support of players such as captain Sergio Ramos and heavyweights Marcelo and Francisco "Isco" Alarcon.
"They believe in me and I believe in them," Lopetegui said. "And that goes to show that we are working well and working hard, and have the motivation to please our fans. We are heading (to Barcelona) with the maximum ambition."
Madrid hasn't lost in its last four visits to Barcelona, although those results came under coach Zinedine Zindane and with Cristiano Ronaldo leading the team that he left in the offseason for Juventus.
Barcelona will also be without Lionel Messi, who is mending a broken right forearm.
That will make this clasico the first to be played without either star since 2007.
Barcelona beat Inter Milan 2-0 this week in its first match since Messi's injury, but despite the strong performance coach Ernesto Valverde rejects the label of favorite against Madrid.
For Valverde, Madrid is even more dangerous when it is desperate for a victory over its top rival.
"We know how Madrid is, the more badly it is hurt, the more dangerous it is," Valverde said. "The crises in teams like Madrid are always blown out of proportion, and then the players step up. There were moments at the start of the season when Madrid was playing brilliantly."
Barcelona, which enters the match in second place at one point behind Atletico, will entrust Luis Suarez to lead the attack.
The only question is whether Valverde will give a second straight start to Rafinha after he scored against Inter, or opt to play forward Ousmane Dembele in Messi's spot.
"We have to be able to play our style, that is the key," Valverde said. "With or without Messi, that is what earned us the league title last year."