Atletico Madrid responded to Real Madrid as they beat Rayo Vallecano 1-0 at the Vicente Calderon to keep pace in the Liga title race without Diego Simeone.
Real had beaten Real Sociedad 1-0 earlier on Saturday, but Atletico remain a point ahead of their local rivals after Antoine Griezmann's decisive strike.
Simeone was absent from the touchline after receiving a ban for his part in the throwing of a ball to disrupt a Malaga attack last weekend, and seven changes from their midweek Champions League win over Bayern Munich resulted in a disorganised first-half showing.
But Griezmann needed just 34 seconds after coming on as a substitute to settle the game, registering his 21st league goal of the season - five of which have come in 1-0 wins.
Attention will now turn to Tuesday's semi-final second leg in Munich as Atletico look to defend another 1-0 lead, given to them by Saul Niguez's stunner, which would take them into a second Champions League final in three years.
Rayo have been outscored by just six teams in La Liga this term, but they could not break down Atletico's iron-cast defence and remain at threat of relegation.
Angel Correa brought a stunning early save out of Rayo goalkeeper Juan Carlos, but it was Atletico's only sight of goal in an otherwise badly disjointed opening half an hour.
Sensing their much-changed opponents were struggling, Rayo began to pour forward with typical reckless abandon, but Miku found Jan Oblak tough to beat and Adri Embarba oddly opted to cross after bursting clear on goal in the left channel.
Correa was Atletico's only bright spark and he brought the crowd to their feet with a stunning flick over his man, but the finish summed up his side's efforts as he scuffed it straight at the keeper.
Koke was introduced in place of Gabi at half-time as Atletico sought control of the game, but Rayo remained on top and Javi Guerra ought to have done better than shoot straight at Oblak after latching on to Bebe's cross.
Simeone's assistant German Burgos responded by throwing Griezmann and Fernando Torres on and the Frenchman had an instant impact, chesting the ball down and smashing a 20-yard half-volley past a helpless Juan Carlos.
Griezmann's addition especially had Atletico in full stride and he zipped down the right flank before squaring for an open Torres, but the in-form striker took the effort on his weaker left foot and could not beat the keeper.
But one was enough for the fourth game in row, with fixtures against rock-bottom Levante and Celta Vigo to come as the title race goes down to the wire.
