Question: Who is the German professional footballer who is the client of Roman Grill?
Context: Roman Grill (born March 1, 1966) is a German former footballer who is now a player agent.  A defender, Grill spent eleven years playing for Bayern Munich's reserve team, and made one first-team appearance, replacing Thomas Helmer in a UEFA Cup match against Benfica in December 1995.  Bayern went on to win the competition that season.  After retiring, Grill worked as a coach with Bayern's youth team, before starting his own player agency in 2006.  His clients include Owen Hargreaves, Philipp Lahm and Piotr Trochowski. 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. Mirko Schuster (born 21 July 1994) is a German professional footballer who plays as a defender for German club SV Waldhof Mannheim. Dženis Burnić (born 22 May 1998) is a German professional footballer who plays as a midfielder for Bundesliga side VfB Stuttgart, on loan from Borussia Dortmund, and the German U19 team. 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." Piotr Artur Trochowski (] , ] ; born 22 March 1984) is a German professional footballer who plays as an attacking midfielder and is currently unattached to a club.  According to his FIFA World Cup 2010 profile he is a playmaker known for "his speed, agility, tricky dribbling and refined technique." Jordan Torunarigha (born 7 August 1997) is a German professional footballer who plays as a defender for Bundesliga side Hertha BSC.  He is the son of former footballer Ojokojo Torunarigha and the brother of current footballer Junior Torunarigha. Daniel Bohl (born 9 June 1994) is a German professional footballer who plays as a midfielder for German club 1.  FSV Mainz 05 II. Mario Gómez García (] ; born 10 July 1985) is a German professional footballer who plays as a striker for Bundesliga club VfL Wolfsburg and the Germany national team.  Gómez joined Fiorentina after spending four seasons with Bayern Munich, which he joined after six years playing for VfB Stuttgart.  At the time the fee was a record for a player transferred in the Bundesliga, estimated to be €30–35 million.  The fee is currently the third highest, after former Bayern teammates Mario Götze and Javi Martínez, respectively.  When Stuttgart became champions in 2006–07, Gómez contributed 14 goals and 7 assists at age 21 and was selected as German Footballer of the Year. Maximilian "Maxi" Thiel (born 3 February 1993) is a German professional footballer who plays for German club 1.  FC Heidenheim in the 2.  Bundesliga.
Answer: Piotr Trochowski