Picking the game of the week for this chilly January weekend was a toss-up. Rayo against Betis will be a well-matched tussle between two sides fighting for European action next season and the locals in Vallecas always provide a "warm" welcome for visiting teams while roaring theirs to the rafters whatever the state of play.
Other home fans could take note.
One stadium where the home support has always been vocal is San Mames. Last season Europe prostrated itself at the feet of a swashbuckling side packed with individual talent. Athletic reached two finals, and lost both rather abjectly.
Coach Marcelo Bielsa's tirade after the King's Cup final found its way out of the locker room.
Javi Martinez left for Bayern Munich. Fernando Llorente appears on his way out too, and the fans turned on him. Results went south and for the first time in several years Athletic looked like losing its record of being one of only three teams never to have tasted the bitter brew that is Segunda Division.
Fortunately for Athletic, the World Cup-winner's ostracism has been ably covered by Aritz Aduriz, picked up from Valencia with the small change of Martinez's €40 million transfer to the Allianz Arena. Aduriz has banged in 12 league goals and did more than most to spare his side's blushes in the King's Cup defeat to lowly Eibar.
And The Lions still have plenty of talent in their ranks, even if Iker Muniain seems to have swapped feet with a Sunday league player recently. Ander Herrera, quiet for much of the season, shone against Betis last week and Gaizka Toquero, a cult figure at the club, has his moments.
Talk of young stars such as Oscar de Marcos and Markel Susaeta being tracked by Europe's top clubs, largely on this showing against Manchester United, has cooled but either can still influence a game from midfield.
Atletico, meanwhile, remains an enigma this season. Diego Simeone's side, Europa League champion last season at Athletic's expense, is still flirting with a title challenge. Atletico's home form is imperious, 11 wins from 11. Its traditional Achilles heel, the defense, is the second-meanest in the league, conceding just 18, 12 away from home.
Joao Miranda and Filipe Luis have been called up to play for Brazil against England next month. Even Diego Costa looks like a footballer again, although he missed the cut himself.
Whether or not Atletico's advances on a league title are going to get past first base is about to be discovered. Barcelona has proven not to be invincible; Atletico now has to show its support that it is not a one-man team.
Radamel Falcao has been ruled out for the next four games after pulling a hamstring against Levante. The Colombian goal machine has scored 18 in the league this season. The next highest scorers for the rojiblancos are Raul Garcia and Arda Turan, with four each. Beyond Falcao in the center forward spot are Costa (two goals) and Adrian (three).
Fortunately for Simeone, there are a few goals in his midfield. And in Koke, Gabi and Arda he has players with an eye for an assist, and the occasional eye-catching goal.
Sunday night's matchup will be a good test for Simeone's away progress, after losses this season to Real Madrid, Barcelona and Valencia on the road.
For Bielsa, it will provide an idea of whether last week's battling performance against Betis was a one-off or a corner turned after three straight defeats.
For the neutral, it should provide a few goals, some amusing chants aimed at Juventus-bound Llorente and insight into the chances of Atletico keeping pace at the top in the absence of its star forward.