This Wednesday, January 9, Real Madrid will try to avenge the loss to Celta Vigo in the first leg of their Copa del Rey tie.
Despite being outplayed for the entire match, a late goal from Cristiano Ronaldo probably saved the tie by keeping the deficit at just one goal.
Los Merengues could move on to the Round of 16 if they score just one goal and keep the Galicians out of goal.
The reigning league champions will be heavy favorites going in, even with all of their internal problems.
The Santiago Bernabeu is one of Europe's most historic stadiums. The awe of looking at the famous white jerseys while tens of thousands of fans are behind them can shake even the best footballer.
Still, Os Celeste have the one-goal advantage and can definitely walk away with the huge upset.
Here are four reasons to think it could actually happen when they head to the Spanish capital this Wednesday.
There is absolutely no debate about who the better or even more in-form player is, but Iago Aspas will be watched just as closely by opposing defenders as Cristiano Ronaldo will be.
The Galician has been one of the league's best players this season and can cause any team trouble, including Real Madrid.
The 25-year old has more goals than any Madrid player except Ronaldo and also has as many assists as last year's European leader, Mesut Ozil.
The difference between Aspas and Karim Benzema, for example, is that the vast majority of football fans couldn't name a single teammate of Aspas' while Benzema is fed by world-class midfielders.
The Spaniard has already had a great start to the new year with a pair of goals against Valladolid.
You can bet Jose Mourinho will focus on him while preparing for this match.
We all know Celta Vigo can beat Real Madrid, because they did it less than a month ago.
What's more, we know they can outplay the reigning Spanish champs pretty comfortably at top form. In the first leg, the Galicians were clearly the better team throughout the match.
If not for a defensive error in the 87th minute, Los Merengues would have been in a pretty deep hole headed back to the capital.
But even in the league match last October, Os Celeste proved that they can hang with the Spanish giants.
The midfield stifled the likes of Mesut Ozil and were not intimidated for one moment by the Galacticos attacking them.
Madrid will certainly be the favorites at the Santiago Bernabeu, but the visitors have already proven themselves capable of pulling off an upset.
Real Madrid house one of the absolute best attacks in the world. However, they will have to be in top form to break Celta Vigo's back line on Wednesday.
In the season so far, the lowly Galicians actually have the better defense when measuring the collective form of the starters.
Hugo Mallo has been the best right-back in the league. If Os Celeste's midfield and attack were as solid as the back four, Celta would be closer to a mid-table team right now.
Of course, those who watched the first two encounters between these clubs know how tough the Galicians can play the reigning champions of La Liga.
In the Copa del Rey match, it was a late defensive slip that prevented the hosts from shutting out the great Madrid in the first leg.
In the league match, it was a tough penalty and a lucky shot (that probably was a cross) that gave Madrid a more comfortable final score than the match actually deserved.
The hosts will likely be in good spirits after their big win over Real Sociedad and should be able to make up the deficit. But the playmakers had better not sleep on the job or they'll be eliminated early.
Real Madrid are currently in third place in La Liga, behind their two biggest rivals and essentially out of the title race.
They failed to top their Champions League group stage (understandably) and put themselves in a very tough spot by getting outplayed by Celta Vigo in the first leg of their Copa del Rey tie.
Perhaps most importantly, the players and coach have been bickering and divided almost since the season began.
Many fans are already calling for Jose Mourinho's resignation due to the awful league showing, despite the fact that the team still have a strong chance of picking up their 10th Champions League title.
If he fails to move on in the Copa del Rey, it would be hard to say his job is secure after this season, especially knowing how Manuel Pellegrini's time at Madrid ended (Mourinho's predecessor).
When comparing talent, depth and sheer financial power, there is absolutely no reason Los Merengues should even be in this predicament in the first place.
If they do end up being knocked out of the tournament, expect the media and fans to (justifiably) go after the entire club and especially their leaders.
The pressure is on.