Borussia Dortmund visit Real Madrid on Wednesday in the first leg of their Champions League quarter-final clash. Last April, BVB lost 2-0 at the Bernabeu, but nonetheless managed to progress to the Champions League final following a 4-3 aggregate victory over Los Blancos.
Real will be looking for revenge for last year's loss, but find themselves facing a very different Dortmund team. Due to the sale of Mario Gotze and a blight of injuries, BVB will likely feature only four of the first XI that faced Real in the first leg last season.
Here's Klopp's most probable first XI to face Carlo Ancelotti's Real.
Goalkeeper: Roman Weidenfeller
One face that Karim Benzema, Cristiano Ronaldo and company will recognize in the Dortmund team is that of Roman Weidenfeller, who faced Real four times in the group stage and semifinals last season. The vice-captain will start in BVB's goal, as per the usual.
Right-Back: Lukasz Piszczek
Like Weidenfeller, Piszczek will be a familiar sight for Real's attackers on the right of the Dortmund defense.
The Poland international spent almost the entire first half of 2013-14 sidelined as he recovered from a pair of surgeries, but has played regularly since the winter break. He was given a rest over the weekend and will be at full fitness on Wednesday.
Centre-Back: Sokratis Papastathopoulos
Although a regular starter this season, Sokratis Papastahopoulos joined BVB last summer as a backup with just three matches of experience in the Champions League from his time as an 18-year-old at AEK.
He's played brilliantly in the absence of Neven Subotic, but will face his greatest task yet as he goes head-to-head with Benzema and the Real attack.
Centre-Back: Mats Hummels
Mats Hummels is the third of four BVB starters from 2012-13 who will play from the start in the first leg on Wednesday. The 25-year-old has spent much of the current campaign sidelined with numerous injuries, but has started BVB's last seven matches in all competitions and should be well-prepared for Real.
Left-Back: Erik Durm
Along with Sokratis, the other new defender in the Dortmund lineup is 21-year-old Erik Durm. The ex-Mainz man was only recently converted from a forward position to that of left-back and now faces the biggest test in his young career as he goes head-to-head with Gareth Bale.
Durm will certainly have his hands full at the Bernabeu.
Defensive Midfield: Sebastian Kehl
Sebastian Kehl was part of the BVB team that reached the Champions League final last season, but only played a combined 13 minutes over the two legs against Real.
The 34-year-old is primarily a bit-part player at this point in his career, but an injury to Sven Bender has made him a starter once more. He will have to roll back the years to keep space to a minimum against a Real team that will look to exploit any area between the BVB midfield and defense.
Defensive Midfield: Nuri Sahin
Nuri Sahin is a familiar face for Real, although not from an opposing position. The Turkey international spent a season at the Bernabeu, mostly as a bench-warmer, before being sent to Liverpool and finally back to Dortmund.
He was part of the BVB side that beat Real in the semifinals last season, but was ineligible to play due to being cup-tied. Like Piszczek, Sahin was given a rest over the weekend and only came on for the final half-hour.
Right Wing: Kevin Grosskreutz
Kevin Grosskreutz played 77 minutes in the second leg of last year's semifinal, replacing the injured Mario Gotze. The 25-year-old is familiar with the threat that Real pose and will most likely start on the right wing, combining with Piszczek to mark Cristiano Ronaldo.
Centre-Attacking Midfield: Henrikh Mkhitaryan
Replacing Gotze, Henrikh Mkhitaryan has big shoes to fill. The Armenia international hasn't enjoyed consistent form this season and will have plenty of pressure on his shoulders as BVB prepare to face Real.
Mkhitaryan has once before met difficult Spanish opposition in the quarterfinals—that ended in a 6-1 aggregate loss to Barcelona. The attacker will aim for a better result at the Bernabeu.
Left Wing: Marco Reus
A muscle injury kept Marco Reus out of the second leg of the round of 16 with Zenit, but the attacker is now back in good form. He netted a hat-trick over the weekend and Klopp will hope the 24-year-old brings confidence to the Spanish capital on Wednesday.
Reus is Dortmund's best chance at stunning the home team.
Centre-Forward: Pierre-Emerick Aubameyang
With Robert Lewandowski suspended, Klopp's options are to use one of BVB's backup strikers, Julian Schieber or Marvin Ducksch, or a tertiary option like Pierre-Emerick Aubameyang.
The Gabon international is perhaps the better option. For lack of defensive ability, he'll likely cede his starting role on the wing to Grosskreutz. As a central player, though, his explosive pace could be decisive against Sergio Ramos and Pepe—especially in the likely event that BVB aim to counter-attack.
While Schieber and Ducksch have some weapons, Aubameyang's trump card is his pace, which will be superlative in value to Dortmund's plans.