Last April, Borussia Dortmund forward Robert Lewandowski demonstrated the complete performance against Real Madrid. It was the semi-final of the Champions League, and the Polish striker scored all four of his side's goals in a 4-1 win at the Westfalenstadion.
Few defenders could have coped with Lewandowski that day. He was exceptional in his all-round play, and his finishing was sublime. He was the focal point of his team's attacks, and he pressed the ball superbly when out of possession.
In the first leg meeting between the two sides last week, the Madrid back line was comfortable in Lewandowski's absence due to suspension. His replacement, Pierre-Emerick Aubameyang, is a quick forward who likes to get in behind, but he didn't cause many problems.
Last night, the return of Lewandowski was evident. He might not have gotten on the scoresheet, but his link-up play and presence gave the two centre-backs a torrid time. Both Pepe and Sergio Ramos aren't exactly slow, and neither player hides from a physical confrontation, so it's surprising that a combination of these attributes caused them significant issues.
"The defence has been doing well and is looking strong. Pepe and Ramos are the reason for the improvement that we have had," added the Italian.
That was down to concentration. The two would occasionally wander, and as a result the team would suffer. Perhaps that's the player's quandary. If they are just against pace or facing a physical matchup, they are happy. They are troubled when there is a combination of the two characteristics.
Since October of 2013, Los Blancos have conceded 31 goals in the league and in Europe, while not conceding any in the Copa Del Rey. Six of those goals were from penalties, while a further nine were scored by strikers of a similar ilk. Fernando Llorente of Juventus got two, Sevilla's Carlos Bacca netted three and former Madrid forward (now at Schalke) Klaas-Jan Huntelaar was another on target.
That doesn't even include goal involvement. One of those forwards could have occupied a defender in the buildup to another goal. Maybe it's more a question of discipline. Ramos and Pepe are always up for the fight with an opponent, but that can lead to losing focus. We have seen how they are easily riled by Atletico Madrid's Diego Costa.
Another factor could be the positions that Lewandowski takes up. He drops in between the lines and pulls out wide to the full-backs in a similar manner to that of a 'false nine.' He has an image of a poacher, but he receives the ball away from goal and creates numerous opportunities himself.
There was one instance last night when Pepe took a step forward and then back, before repeating the process with the rest of his back four in a line. He was uncertain whether to close the gap and leave space behind him or drop off and allow Lewandowski the chance to run at him.
In last year's semi-final, he received the ball only twice in the area during the entire match, yet he scored four times, via FourFourTwo Stats Zone. It's amazing how far away he drifts, and it's that positioning that troubles centre-backs.
It's not just the responsibility of the defenders, though. The whole team has to work together. The holding midfielder obviously has a huge role. Xabi Alonso made three fouls in front of the defence and was lucky to not have been dismissed.
It will be interesting to see if Ancelotti notices this pattern and if he takes any action to rectify the situation. He might choose to change a defender or alter the defensive midfield, depending on the type of forward they come up against.