Atletico Madrid rescued a 2-2 draw away to Athletic Bilbao thanks to a brilliant strike from Antoine Griezmann.
The France star blasted home from 25 yards to stretch his side's unbeaten run against Athletic to seven matches after the home side had come from behind to take the lead at San Mames.
Koke's cross bounced beyond Griezmann and into the far corner to give the visitors a promising start, as they looked to react to victories for top two Real Madrid and Sevilla this weekend.
Athletic, however, responded with a stylish equaliser from Inigo Lekue before De Marcos powered in a header in the second half to cap one of their better performances of the season.
Atleti pressed in the closing stages but gave goalkeeper Gorka Iraizoz little to be worried about, until Griezmann drove into space and rifled a shot in off the base of the post to secure a share of the spoils.
Ernesto Valverde's side move to within two points of sixth-place Villarreal, while Atleti close to within eight of leaders Madrid - although their city rivals' game in hand means any title charge from the 2014 champions still looks unlikely.
San Mames was in fine voice before kick-off but was silenced in only the third minute, as Koke's clever low cross from the left bounced all the way into Iraizoz's bottom-right corner after Griezmann tried to flick it on its way.
Raul Garcia came close to an equaliser against his old club, as Miguel Angel Moya misjudged his low drive from 25 yards and watched the ball strike his midriff before rolling wide of the left-hand post.
Yannick Carrasco missed a good chance to double the lead, dragging a left-footed shot wide from a tight angle after superb play from Koke and Griezmann released the Belgian on the counter-attack.
That miss proved to be costly when, four minutes before the break, Inaki Williams fed Lekue on the edge of the box, where he worked space before blasting the ball high into the net beyond Moya.
And 11 minutes into the second half, Athletic completed the turnaround. Garcia clipped a cross from the right towards the centre of the box, where De Marcos rose completely unmarked to head emphatically home.
Simeone responded with a bold attacking change, introducing Fernando Torres, Nico Gaitan and Angel Correa from the bench, as he looked to secure a fourth away win in a row against an Athletic side who have been blighted by inconsistency this season.
Correa fizzed a shot wide of the right-hand post but Atleti's use of the ball in the final third was too often careless as they frantically chased a way back into the match.
But Griezmann, who had endured a quiet second half, proved to be Atleti's hero once more with 10 minutes of normal time to play. Gathering a pass following a good run from Torres, he worked some space before driving a left-footed shot that looked to take a slight deflection on its way into the bottom-left corner.