Atletico Madrid slumped to a 1-0 defeat at home to Real Betis on Sunday in La Liga, three days after thrashing the Andalusian side in the Copa del Rey.
Antony's first-half strike split the teams, earning his side revenge and leaving Atletico, third, 13 points behind leaders Barcelona after they beat Mallorca on Saturday.
Betis, fifth, continued their push towards the top four, now trailing fourth-placed Villarreal by four points, although they have played two more matches than the Yellow Submarine.
Diego Simeone's Atletico waltzed into the Copa del Rey semi-finals with a hefty 5-0 win at Betis on Thursday, but this was a far closer affair at Atletico's Metropolitano stadium.
"It's a tough defeat to take after the great game we had in the cup, we weren't as good as the other day," admitted Atletico captain Koke to Movistar.
"They set up a lot tighter at the back... We had very few chances and they played a great game."
Betis coach Manuel Pellegrini made five changes to the team which crumbled at home and his side were determined to prove a point in the Spanish capital.
Atletico stopper Jan Oblak denied Cedric Bakambu, while at the other end Julian Alvarez, struggling for form, was kept at bay by Betis' Alvaro Valles.
Betis took the lead in the 28th minute through their key player Antony, who took an early shot from 20 yards which caught out the usually impeccable Oblak at his near post.
It was the Brazilian winger's 10th goal of the season across all competitions and enough to claim all three points.
Simeone hooked Alvarez at half-time for Alexander Sorloth, but his team could not find a way back.
Atletico had the ball in Betis' net with 15 minutes to go when Diego Llorente headed Giuliano Simeone's cross into his own net, but Antoine Griezmann was judged to be fractionally offside and interfering with play.
Former Atletico midfielder Rodrigo Riquelme could have doubled his team's advantage late on but Oblak read his chipped effort and plucked it out of the sky.
"The result (in the cup) was very, very hard to take... We had to correct a lot of things in these two days," said Betis midfielder Alvaro Fidalgo.
Real Madrid, second, visit Valencia later on Sunday.