It was research ahead of games which made Pierluigi Collina the most respected referee in football. The Italian would spend hours in the build-up to games watch footage of matches, looking for tactics employed by teams which he could swiftly stamp out when he was on the pitch.
Speaking on NBC's Men in Blazers podcast, former Premier League referee Mark Clattenburg explained how Collina 'changed his refereeing career.'
It was simple: he was my observer in Bayern Munich vs Barcelona [2015 Champions League semi-final second leg] reviewing my performance.
Nervous? It was a nightmare because you never drink in his company and I always liked a beer but you respected the man.
When he came to this game, he said, 'Mark, have you prepared for this match?' I said, 'I've watched the first leg six times.' He said, 'Really?' and he opened his laptop and asked, 'Have you seen this tactic by Bayern Munich?' I said, 'What are you on about?'
The small player, Thiago, from Bayern Munich was deliberately standing in an offside position but not being involved in play. He would block the path of Pique from heading the ball in attacking phases. This was to create the space for the big players of Bayern Munich to attack the small players from Barcelona because only had one tall player. It was a clear tactic.
In the second leg, after 13 minutes, I gave a small free kick and the players thought I was unbelievable. They couldn't understand how I knew this tactic.
Clattenburg went onto employ Collina's methods in the Premier League.
When I started to become the best referee or one of the best referees in the world, I knew the tactics before clubs even thought about them.
In the Premier League, for example, blocking in the penalty area, I was already telling the players that I'm watching the block. Before it even happened the players are like, 'Woah, the referee knows what we're going to do here.'