Question: What professional footballer who plays as a midfielder for Aston Villa and for England U21 has played in the HKFC Soccer Sevens?
Context: Jerome Marie Thibault Stephanie De Clarens (born 12 May 1989) is a French professional footballer, who plays as a midfielder for the HKFC Soccer Section in the Hong Kong First Division League. Jack Grealish (born 10 September 1995) is a professional footballer who plays as a midfielder for Aston Villa and for England U21.  He joined Aston Villa at the age of 6, and made his debut for the club in May 2014, following a loan at Notts County.  Eligible to represent either England or the Republic of Ireland internationally, Grealish was capped by Ireland up to under-21 level before confirming his decision to play for England in April 2016.  He played for the England under-21 side for the first time in May 2016, winning the 2016 Toulon Tournament. André Green (born 26 July 1998) is an English professional footballer who plays as a winger for Aston Villa. He is a life long Aston Villa fan and is a fan favourite at Aston Villa.  He has represented England from under-16 to under-19 level. Earl Delisser Barrett (born 28 April 1967) is an English former footballer who played in the Football League and Premier League for Manchester City, Chester City, Oldham Athletic, Aston Villa, Everton, Sheffield United and Sheffield Wednesday.  He played mainly at right back though could also adapt to a central defensive role.  He also gained three England caps while playing at Oldham and Aston Villa.  The £1.7m Aston Villa paid for him in February 1992 remains, as of 2014, Oldham Athletic's record transfer receipt. The HKFC Soccer Sevens, formerly known as the International Soccer Sevens, is an annual invitational seven-a-side football tournament which is organised and hosted by Hong Kong Football Club.  Held since 1999, many young professional players have made a name for themselves in the tournament including Premier League players Gabriel Agbonlahor, Jack Grealish, Rolando Aarons, Glen Johnson, Anton Ferdinand, David Bentley and Marc Albrighton, as well as Scotland internationals Shaun Maloney, Craig Beattie and Chris Burke. Aston Villa Football Club ( ; nicknamed Villa, The Villa, The Villans and The Lions) is a professional football club in Aston, Birmingham, that plays in the Championship, the second level of English football.  Founded in 1874, they have played at their current home ground, Villa Park, since 1897.  Aston Villa were one of the founder members of the Football League in 1888 and of the Premier League in 1992. Stiliyan Alyoshev Petrov (Bulgarian: Стилиян Альошев Петров, born 5 July 1979) is a former Bulgarian professional footballer who played as a midfielder.  Petrov joined Celtic from CSKA Sofia in 1999, and won ten trophies in his time at Celtic Park, including four Scottish Premier League titles.  In 2006, he moved to Aston Villa in the Premier League, along with his former manager Martin O'Neill.  Petrov became club captain at Villa Park, and was an inductee to the Aston Villa Hall of Fame in 2013.  In addition he is Bulgaria's all-time most-capped player with 105 appearances for the side. Gary Gardner (born 29 June 1992) is an English footballer who plays as a central midfielder for Barnsley on loan from Aston Villa.  A product of the Aston Villa Academy, Gardner has spent brief loan spells at Coventry City, Sheffield Wednesday, Brighton & Hove Albion and Nottingham Forest.  He has made a number of appearances at different international levels for England.  He is the younger brother of current Birmingham City midfielder and former Aston Villa team-mate Craig Gardner. Gershom Cox (September 1863 – November 1918) was an English professional footballer who played as a full-back for Aston Villa from 1888 to 1893.  He made 102 first-team appearances for Aston Villa in all competitions.  After his years at Aston Villa he went as Player/Coach for Gravesend in Kent. Gareth Southgate (born 3 September 1970) is an English football manager and former player who played as a defender or as a midfielder.  He is currently the manager of the England national team.  He won the League Cup with both Aston Villa and Middlesbrough (in 1995–96 and 2003–04 respectively, and as captain), and captained Crystal Palace to win the First Division championship in 1993–94.  He also reached an FA Cup and UEFA Cup final as a player, and made 57 appearances for the England national team, featuring in the 1998 FIFA World Cup and both the 1996 and 2000 European Championships.  His playing career ended in May 2006 at the age of 35, and after more than 500 league appearances, he was subsequently appointed Middlesbrough manager.  He served as manager of Middlesbrough from June 2006 until October 2009, then managed the England U21 team from 2013 to 2016, before becoming the England national team manager in 2016.
Answer: Jack Grealish