Arsenal teenager was back in action after a two-week lay-off.
Arsenal's Krystian Bielik could not prevent the club's under-21 side from losing against West Brom on Tuesday afternoon.
The Polish international had missed the team's last match after being injured against Reading earlier this month.
Bielik was a January signing from Legia Warsaw, and has been touted to eventually become a first team player in defensive midfield.
The teenager had been playing in central defence recently, with Jack Wilshere, Mikel Arteta, and Abou Diaby needing game time and taking up spots in midfield.
Against West Bromwich Albion's under-21 side he was back in his preferred role in midfield, but was powerless to stop Adil Nabi running riot, with the Baggies prospect netting a hat-trick in a 3-0 win.
Results are not necessarily important for the team, who are not at this stage challenging for any titles, instead it is about getting players like Bielik more game time.
The fact his injury was just a brief lay-off was a positive, for he had only just made the step up to the under-21s from the under-18s when he suffered it.
The more he can learn now will stand him in good stead for the club's pre-season tour, when the chances to play representing the first team may come his way, and he will have the perfect opportunity to impress manager Arsene Wenger.