The purpose of this study was to elicit the activity of assistant referees during football game when they judge duels. It investigated their lived experiences, in order to understand the preoccupations they had to participate in decision making. Six professional football matches were observed and twelve self-confrontation interviews conducted. Findings showed the participation of assistant referees in decision making depends on preoccupations concerning the central referee's priority. They constructed their judgement according to the central referee's perceived contextual judgement. A latent intention to coordinate their activity with the central referee judgement is embedded in the assistant referees' preoccupations.