Was this week's stirring 3-2 comeback defeat of Manchester City the beginning of Real Madrid's recovery or just a dramatic flash in the pan?
That is the question that will be in the autumn Madrid air on Sunday (Monday AEST), when Real makes the short trip south to face local rival Rayo Vallecano.
Defender Pepe said just hours after the memorable defeat of City: "Things are going to change from now on. Now everyone is going to see a different Real Madrid."
Just as well, because Real has already dropped eight points - in its worst start for years - and is 12th in the table.
Astonishingly, Rayo is six places above Real, with three points more.
Rayo right-back Tito said: "We always play to win, especially at home. We might do things well or badly, but we are going to go for the game.
"We are expecting the best version of Real Madrid, the one that played so well on Tuesday. It's true they haven't got into their stride in the league but they will soon find their rhythm."
Real coach Jose Mourinho raised eyebrows on Tuesday (Wednesday AEST) by benching defender Sergio Ramos.
Now he will have to decide whether to bring him back or stick with teenager Raphael Varane.
Mourinho will also have to decide whether to start with playmakers Luka Modric and Mesut Ozil - who came off the bench and turned the game against City around - or stick with physical battlers Sami Khedira and Michael Essien.
Sunday's (Monday AEST) other games are Mallorca v Valencia, Levante v Real Sociedad, Atletico Madrid v Valladolid and Athletic Bilbao v Malaga.
Second-placed Malaga is on Cloud Nine after its inspirational Champions League debut this week, thrashing Zenit St Petersburg 3-0.
Bilbao, meanwhile, will have to decide whether to give Fernando Llorente his first start after his August attempt to leave.
The Spain striker will surely be greeted by San Mames with more jeers than cheers.
Sunday's (Mondy AEST) big game will see runaway leader Barcelona at home to Granada, which is third from bottom.
Barca defender Gerard Pique will be missing after damaging his left foot in Wednesday's (Thursday AEST) 3-2 comeback defeat of Spartak Moscow, whilst usual partner Carles Puyol is out for a month with a knee injury.
This means newcomer Alex Song will make his first start, alongside Javier Mascherano.
Also on Saturday (Sunday AEST), bottom team Osasuna will visit Zaragoza while Celta Vigo hosts Getafe and Betis take on Espanyol.
The fifth round of games will finish on Monday (Tuesday AEST) with Deportivo La Coruna at home to Sevilla.
Barcelona captain Carles Puyol is to undergo knee surgery to remove a cyst, the club says.