Barcelona have reportedly taken an interest in signing three players from Bayer Leverkusen.
Ernesto Valverde's side have made an unbeaten start to the La Liga campaign but with funds still available from the sale of Neymar, targets are seemingly being identified ahead of the upcoming transfer windows.
According to Sport, that resulted in Barcelona sending scouts to Bayer Leverkusen's Bundesliga fixture with Wolfsburg, a game which ended in a 2-2 draw.
Twenty-one-year-old Tah has made 77 appearances since breaking into the first team in 2015, while highly-rated German compatriot Brandt - who has previously been linked with Liverpool - has 22 goals to his name in 137 outings.
Bailey - who attracted interest from Manchester United before signing for Leverkusen in January - has made just three starts and 14 substitute appearances.