Antoine Griezmann hit the woodwork and missed a penalty
La Liga leaders Atletico Madrid's club-record 15-game winning run has come to an end with a surprise defeat at neighbours Leganes.
Atletico had a chance to at least keep their unbeaten record going when they were awarded a last-minute penalty, but their all-time record scorer Antoine Griezmann put the spot-kick wide.
Diego Simeone's side had won every game since a loss at Real Betis on 27 October.
But the crucial goal on Saturday came when Leganes centre-back Matija Nastasic headed in from Dan Raba's cross.
Julian Alvarez and Griezmann had both hit the woodwork in the first half with the game goalless.
Real Madrid, who are just one point behind Atletico, can go top if they win or draw at home against Las Palmas on Sunday (15:15 GMT).
Atletico captain Jan Oblak told DAZN: "We didn't come in well. There was a lack of energy, not enough.
"It was our own issue. It shouldn't have to happen. With a bit more energy we could have turned it around.
"We didn't play well but we should have our head up. After 15 games, we've lost."
Leganes are 15th, three points above the relegation zone, after the surprise win.
