Jose Mourinho has said he was unhappy with Manchester United coach Giovanni Cerra ahead of Thursday's 1-0 victory over Zorya Luhansk because his instructions left Paul Pogba confused.
Mourinho marched from the touchline to the dugout ahead of the kickoff to remonstrate with Cerra and slammed the coach's folder shut.
The Portuguese, who also appeared unhappy when addressing assistant Rui Faria on the touchline, told BT Sport after the game that Zorya Luhansk had made changes to their lineup that had left United midfielder Pogba unsure over his role.
"It was, you know, set pieces, organisation," he said. "They changed their team before the game and Paul was a bit confused with the changes and obviously I want my assistants to take care of all the details."
Former United midfielder Owen Hargreaves, now working as a pundit for BT, said: "That shows his attention to detail. He is a perfectionist."
United secured victory in the Europa League fixture after Zlatan Ibrahimovic was able to head home from a Wayne Rooney miscue.
Rooney had come off the bench in the match and Mourinho said afterwards that the club captain "gave me what the team needed at that time."
The win leaves United third in Group A, a point behind leaders Fenerbahce, after they lost their opening match 1-0 at Feyenoord.