So I didn't read the article but 25 years ago I was part of a group of 100 15-17 year olds in the US recruited by Liverpool to see if we were good enough to go over seas to their academy to finish up school. So I've been following them ever since.

What I remember reading in their 2nd game against Barcelona is the data team told the coaches about how Barcelona was slow to setup for set pieces mostly corner kicks. The ball boys are all academy players and the coaches told the ball boys on corner kicks to get the ball to the Liverpool player as quickly as possible.

I believe it went as far as them having more ball boys then usually to just have 4 of them sit with a ball in each corner.