Coming just a few days after a heated La Liga confrontation, the first question to be answered will be to what extent the Periquitos are prepared to adopt the same roughhouse tactics—tactics that got right under the skin of the Barcelona players and management team.
Not that new Espanyol manager Constantin Galca and his side will be concerned. That's a league point well won. Eastbridge provided some key stats:
FT stats: Espanyol 0-0 Barcelona Possession - 28%-72% Shots on target - 1-2 Off target - 2-5 GK saves - 2-1 Fouls - 22-11 Yellow Cards-5-21/2/2016, 4:52:46 PM
Barca need to understand that the dark arts of the game are another way of winning, and for all of the Blaugrana's pretty football, sometimes you've just got to mix it.
Perhaps that's why the notion of signing Juventus' Paul Pogba hasn't completely disappeared. A player who doesn't mind putting their foot in would at least cure some of Barca's ills in games such as the one that played out at Cornella El-Prat this past weekend.
With a potential nine games to play in January, including a fixture against title rivals Atletico Madrid, Luis Enrique needs to guard against weariness among his troops.
There's a certainty to a debut or two being made, and to that end we will probably see rotations coming into play here.
It's an intriguing matchup. If the visitors can again take the game to their more illustrious neighbours, there's no reason another draw won't be on the cards, leaving them in the box seat for the return.
Enrique's men would be better served in getting the job done on the night so that rotations in the second leg don't affect the outcome.
Date: Wednesday, 6 January
Time: 7:30 p.m. GMT/2:30 p.m. ET
Venue: Camp Nou, Barcelona
TV Info: beIN Espanyol (U.S. only)
Live Stream: beIN Sports Connect (U.S. only)
Espanyol did wonderfully well playing Galca's favoured formation of 4-2-3-1, and although that's probably a little too attack-minded for a date at Camp Nou, the manager will live or die by his selections.
How often have we seen a team sit back and invite pressure and then be destroyed by a far superior XI.
Credit to the manager for devising a strategy, albeit an unappealing one for Barca, that gave them the opportunity to impose their own game and forced Barca into situations that were clearly uncomfortable.
Felipe Caicedo will lead the line once again, and he might find that against a less than fully fit Thomas Vermaelen, he gets more change from the Belgian than he did against Gerard Pique and Javier Mascherano.
Pique is likely to be the only member of the back four to keep his place as Luis Enrique affords Aleix Vidal his debut and gives Adriano another run out on the left side.
The manager might change his staff around, but he won't play around with the tried-and-trusted Barcelona 4-3-3—a formation that continues to serve the Blaugrana well and one in which all players are fully versed.
Marc-Andre ter Stegen gets the gloves back on again after being overlooked at the Club World Cup last month, a decision that is likely to have not gone down well with the young German.
Marco Asensio was lively in the game at the weekend, but pushing Javier Mascherano forward into direct combat with the tricky youngster should limit the damage he can do.
Given that he's only on loan from Real Madrid, new-man-in-charge Zinedine Zidane could be casting a few glances over this game to assess the merits of a player who's winning rave reviews for his performances.
Burgui was a little disappointing against this opposition, but Hernan Perez had more luck down his side of the pitch.
If Vidal and Arda Turan have used their training time wisely, we should hopefully see the fruits of an emerging right-hand-side partnership and one in which Burgui and Pape Diop will be worked extensively.
Andres Iniesta might need to play a little deeper for longer periods to stop Espanyol from overloading in important areas of the pitch. Joan Jordan hasn't been in the best form, but if he's given space to work, he'll be able to pick out a pass for his colleagues to capitalise on.
Can Victor Alvarez, Enzo Roco, Alvaro Gonzalez and Javi Lopez shut them out for a second successive 90 minutes?
Pau will again get the nod in goal after a sterling effort against Barca last time out.
Player to Watch
Felipe Caicedo was a real handful for the Barcelona defence in the league match.
Despite not getting on the scoresheet, he was a constant thorn in the side for Gerard Pique and Javier Mascherano in particular.
A mixture of size and strength makes the ex-Manchester City front man a very awkward customer indeed, and the back four need to ensure he is "looked after" from the first whistle.
If there is any hint of weakness there from the hosts, Caicedo will exploit it. He won't pass up another 90 minutes of opportunities, and the away goal could be very costly for Barca.
Barca's best hope of keeping his influence to a minimum is to ensure the ball stays down the opposite end.
Even with reserves on the pitch, Barca still have enough about them as a team to be able to keep the ball well at home.
Forcing their opponents to chase and harry will eat into their energy reserves. Therefore, the last 10 minutes could be crucial.
Arda Turan has waited patiently for this moment for the last six months.
A caged lion at the best of times, the Turkish international is likely to put his heart and soul into his debut performance for the Blaugrana.
Woe betide Pape Diop if he's either not on his game here or if he takes a hard line throughout as he did with Ivan Rakitic.
Turan isn't cut from the same cloth as the Croatian, and he'll ensure Diop is kept on his toes throughout.
Never one to be frightened of a battle royale, Turan has excellent technical qualities too, which can often be overlooked because of the player's tendency to get involved and stand toe-to-toe with his opposite number.
It took until the 88th minute for Diop to receive a yellow card in the league match, but that was more as a result of below-par officiating than the player staying out of trouble.
Turan will force him to engage, and a short fuse could see a much-earlier admonishment, handing the impetus to the home side.
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