The 30-man squad flew to Birmingham on Monday before training early evening in the Midlands, with Fermín Lopez continuing his recovery from injury.
The midfielder missed out on Spain’s World Cup success after breaking his foot against Real Betis in May.
Flick’s squad is a mix of senior players, along with others from Barcelona B and the under-19s, including forward Orian Goren who only turned 17 in March.
Netherlands midfielder Frenkie de Jong has travelled despite a knee injury which was expected to keep him out for months.
The 29-year-old damaged the medial collateral ligament in his right knee at the World Cup.
Another surprise inclusion is Marc-Andre ter Stegen, who has been expected to move to Ajax on loan. No deal has been struck so the German goalkeeper has travelled to England and could face Birmingham in Friday’s game.
Barca had a double session on Tuesday and are training on the pitch reserved for the England senior team.
After their trip to St Andrew’s, Barca will take on Preston behind closed doors at St George’s Park next Monday.
Paul Heckingbottom’s side started their pre-season with a 4-1 win against Northern Premier League Premier Division side Bamber Bridge at the start of the month.
Barca also travel to Italy for two 45-minute matches against Nottingham Forest and Udinese in the Friuli Venezia Giulia tournament on 8 August.
Barcelona squad: Ter Stegen, Fort, Balde, Araujo, Cortes, Guille Fernandez, Toni Fernandez, Farinas, Abdelkarim, Tommy, Xavi Espart, Yaakobishvili, Adeyemi, Christensen, Fermin, M Casado, Gerard Martin, Roony, Tunkara, Torrents, Bernal, Gonzalez, Kluivert, Szczesny, Goren, Gistau, Diarra, Pesquer, Rodriguez, De Jong.
