Barcelona reportedly scouted Bayer Leverkusen trio Jonathan Tah, Julian Brandt and Leon Bailey during the club's Bundesliga clash with Wolfsburg on Sunday.
Sporting director Robert Fernandez and chief of scouting Urbano Ortega were at the game, which finished in a 2-2 draw, with the club also apparently interested in Benjamin Henrichs, according to Sport.
Defender Tah is still just 21 but is one of the most promising young centre-backs in the Bundesliga and has already been capped by Germany at senior level.
Barcelona may be searching for more youthful options at centre-back, with Javier Mascherano already 33 and approaching the end of his career, while Gerard Pique will turn 31 next year.