Barcelona chief Ariedo Braida was in Germany on Friday night.
The Italian attended Schalke's clash with Bayer Leverkusen, reports BILD.
It's understood Braida was making a check on Schalke's young midfieder Leon Goretzka and Bayer defender Jonathan Tah.
Braida confirmed Barca's interest in Goretzka, though insisted it was too soon to consider whether a bid would be made. The youngster's S04 deal expires in June.
"He is certainly a great player, but for Barcelona it is too soon," said Braida.
"I travel around the world in search of great talent, but our demands are extremely high."