Question: Which starting centre back was teammates with Lazaros Christodoulopoulos?

full_context: Document 1: Luka Modrić: Luka Modrić (] ; born 9 September 1985) is a Croatian professional footballer who plays for Spanish club Real Madrid and captains the Croatia national team. Modrić plays mainly as a central midfielder but can also play as an attacking midfielder or as a defensive midfielder, usually deployed as a deep-lying playmaker.
Document 2: Łukasz Piszczek: Łukasz Piszczek (] ; born 3 June 1985) is a Polish footballer who plays for German Bundesliga club Borussia Dortmund and thePoland national team as a right back, having previously played for Hertha BSC and Zagłębie Lubin. He has been capped over 50 times by Poland at international level from his debut in 2007, and was included in the nation's squads for three European Championships.
Document 3: Lazaros Christodoulopoulos: Lazaros Christodoulopoulos (Greek: Λάζαρος Χριστοδουλόπουλος ; born 19 December 1986) is a Greek footballer who plays for AEK Athens and the Greek national team. His main strengths are his technique, pace and acceleration with the ball. Like his Greek teammate Sokratis Papastathopoulos, his surname is too long to fit on his shirt, so his shirt reads Lazaros instead.
Document 4: Neven Subotić: Neven Subotić (] ; Serbian Cyrillic: Heвeн Cубoтић; born 10 December 1988) is a Serbian footballer who plays as a centre back for the German Bundesliga club Borussia Dortmund. He made his first-team debut in the 2006–07 season for 1. FSV Mainz 05. In 2008, he signed with Borussia Dortmund.
Document 5: Sokratis Papastathopoulos: Sokratis Papastathopoulos (Greek: Σωκράτης Παπασταθόπουλος , ] ; born 9 June 1988) is a Greek footballer who plays as a starting centre back for German Bundesliga club Borussia Dortmund and the Greek national team. Since the surname Papastathopoulos is too long to print on the back of most shirts, the name Sokratis is usually displayed and is the singular name that he is best known by in the football world.
Document 6: Mamadou Sakho: Mamadou Sakho (born 13 February 1990) is a French professional footballer who plays as a centre-back for Premier League club Crystal Palace and the France national team. He is known for his tackling ability and his passing accuracy.
Document 7: Nike Mercurial Vapor: The Mercurial Vapor is a football boot manufactured by Nike. The boot is known for being lightweight. Because of this, the boot is endorsed by many players for whom speed is part of their game, notably wingers or strikers, such as Cristiano Ronaldo, Franck Ribéry, Luiz Adriano, Zlatan Ibrahimović, Didier Drogba, Jesús Navas, Luka Modrić, Arturo Vidal, Douglas Costa, Xherdan Shaqiri, Raheem Sterling, Stephan El Shaarawy, Eden Hazard, Alexis Sánchez, Carlos Bacca and Philippe Coutinho, among others.
Document 8: Christos Xenitopoulos: Christos Xenitopoulos (Greek: Χρήστος Ξενιτόπουλος ; born 1 June 1990) is a Greek footballer, who currently plays for Ethnikos Piraeus F.C. in the Football League 2 as a Left back . Xeni is an enthusiased left back with a very good left foot. He is also known as a great free kick and corner taker scoring from the corner spot 3 times.
Document 9: Per Mertesacker: Per Mertesacker (] ; born 29 September 1984) is a German professional footballer who plays as a centre back for Premier League club Arsenal. He also played for the Germany national team but retired in August 2014 after winning the World Cup. Mertesacker is a youth product of Hannover 96 and he made his senior league debut in November 2003. He was soon dubbed "the Defence Pole" (""die Abwehrlatte"") by German tabloids and gained a reputation for his good disciplinary record, going 31 Bundesliga games without being booked. Since joining Arsenal, their fans have nicknamed him "the BFG", which is short for "Big Fucking German" and an allusion to Roald Dahl's "The BFG" due to his height. He has been described as an imposing, reliable, dominant and an accomplished defender.
Document 10: Nikos Sofis: Born in Munich, Germany, and growing up close by to Frankfurt, he attended the Frankfurt International School from where he graduated in 2011. In 2013, he attended the EU Business School in Barcelona, Spain, where he began his Sports Management studies. Since 2014, he continues his studies at the American College of Greece in Athens. He is fluent in Greek, German, and English.
Document 11: Jérôme Boateng: Jérôme Agyenim Boateng (] ; born 3 September 1988) is a German professional footballer who plays as a defender for German club Bayern Munich and the Germany national team. A versatile defender, Boateng primarily is a centre-back, although he can also play as a right-back. Physically strong and composed in possession, he has garnered a reputation as a tough-tackling defender, with good passing and an ability to read the game, and is considered to be one of the world's best at his position.
Document 12: Mario Götze: Mario Götze (] ; born 3 June 1992) is a German professional footballer who plays as an attacking midfielder for German Bundesliga club Borussia Dortmund and the Germany national team. Although his favoured position is that of a playmaker. Götze possesses speed, technique, dribbling skills, and playmaking capabilities. In 2010, German Football Association's then technical director Matthias Sammer described Götze as "one of the best talents Germany has ever had."
Document 13: Lazaros Fotias: Lazaros Fotias (; born 26 April 1991 in Giannitsa) is a Greek footballer currently playing as a centre back for Slovak club Topvar Topoľčany.
Document 14: Ezequiel Lavezzi: Ezequiel Iván Lavezzi (] ; ] ; born 3 May 1985) is an Argentine professional footballer who plays for Chinese club Hebei China Fortune and the Argentina national team as a forward. He is known for his pace, hardworking style of play, technique, creativity, and dribbling ability; although he is usually deployed as a winger, he has also been used as a second striker or as an attacking midfielder on occasion.
Document 15: Athanasios Kostoulas: Athanasios Kostoulas (; born 24 March 1976) is a former Greek football player. A determined tackler with timing to match, Kostoulas preferred to operate as a defensive midfield player but has played in every position across the back line.
ground_truth: Sokratis Papastathopoulos