Barcelona host Espanyol at the Nou Camp for their second meeting in five days. This will be followed within a week by the second leg.
It's fair to say that by then, each team will know the other inside out but as we approach this one, Espanyol manager Constantin Galca will be the happier of the two.
His roughhouse tactics didn't go down too well with the opposition, and the referee's failure to clamp down on the same gave the Blaugrana even more reason to be upset.
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It's doubtful that the visitors will shy away from the darker arts in this one either and Barca will certainly have to be at their best to take the advantage back to the Power8 Stadium.
Let's take a look at three things that might shape the outcome of this one...
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If there are two players that will be giving their absolute all on Wednesday night, it will be Arda Turan and Aleix Vidal.
Two Barcelona players that have sat in the stands for the best part of six months waiting to make their official debuts.
Now that Barca's transfer ban has been lifted by FIFA, those two will be like caged lions. Turan was never a shrinking violet at the best of times and this game gives him licence to fight fire with fire, something that perhaps Barca were lacking in the league match.
Both will give Barca impetus across the width of the pitch and Vidal's speed down the right channel will be the equal of Jordi Alba on the opposite side.
Espanyol evidently will have a bit more to think about.
The visitors could be encouraged by the potential amount of games that Barca will need to play during January.
Should they overcome Espanyol, the Blaugrana will have nine games to play before the end of the month, culminating in a potentially decisive league game against Atletico Madrid.
The thought of rotation can't be too far from Luis Enrique's mind therefore, but the Periquitos showed that they were more than a match for Barca's first XI so a potential switcharound arguably plays right into their hands.
Is Lucho damned if he does and damned if he doesn't?
History against Espanyol
Just one win at the Nou Camp in over ten years. That is the history that faces Espanyol when they step out onto the turf.
For all of their hustling and harrying in a number of games between the two sides, they've never really been able to convert their dominance into a win.
A goalless draw would even suit Barca here, knowing that away goals count double.
Expect it to be another feisty encounter. Espanyol have to stop reverting to type if they want to take this one.
Who should Barcelona start with in tonight's game? Give YOUR opinion in the comment box below!