Luciano Vietto's first goal for Atletico Madrid secured a 1-1 derby draw seven minutes from time and stopped Real Madrid from moving to the top of La Liga.
Karim Benzema headed his seventh goal in eight appearances this season in the ninth minute and looked to have settled a typically feisty tussle at the Vicente Calderon, where his France international team-mate Antoine Griezmann had a first-half penalty saved for the hosts.
Griezmann partly atoned for that error by having a hand in the equaliser – making enough of a nuisance of himself at the near post for Jackson Martinez's low cross to squirm beyond goalkeeper Keylor Navas for his fellow substitute Vietto to convert from close range.
Vietto's former club Villarreal lost 1-0 to Levante earlier on Sunday, presenting the opportunity for Real to take top spot.
But Rafael Benitez's team could not get over the line and lie a point off the pace in second after extending their winless run at the home of their near neighbours to six matches.
Cristiano Ronaldo headed wide early on from Luca Modric's left-wing cross but it was from the opposite flank that Real took the lead.
Atleti's response was strong, with a fired-up Angel Correa to the fore.
Some ragged Real defending gifted Atleti a golden opportunity to equalise from the spot in the 20th minute – Sergio Ramos briefly looked to have retrieved the situation but took a heavy touch and clattered through Tiago.
But Griezmann's well-struck effort was at a favourable height for Navas, who sprung to his left and pushed the ball to safety.
The former Liverpool striker then had an attempt blocked before making way for Jackson Martinez in the 64th minute.
Vietto appeared crestfallen when he wasted a good headed chance in the 81st minute but the Argentine amends three minutes later – his compatriot Diego Simeone leading the boisterous celebrations from the dugout before Martinez was denied by Navas as the hosts almost snatched another famous triumph.
