Valerien Ismael explained he dropped key midfielder Imran Louza for disciplinary reasons ahead of Watford’s 1-0 defeat at home to Blackburn.
The Morocco midfielder is understood to have been punished for poor time-keeping, arriving late for a training session.
Louza was introduced as a half-time substitute but it was from his error that Ryan Hedges went on to score the game’s only goal.
Ismael made it clear afterwards that stamping down on lax discipline was top of his agenda as Watford’s new manager.
“When we came we set rules with the players and everyone has to respect the rules, it’s as simple as that,” he said.
“Imran knows exactly why he was on the bench today. You have to understand as well I’m not happy to take some decisions but I have to take action when people don’t respect the rules.
“I want to play my best team in the league. It was an internal situation, now everything is clear so we move on. I don’t need to go into details, it is enough to say he was on the bench.”
Hedges won it for Rovers in the 72nd minute. Louza misplaced a pass that allowed Rovers substitute Sam Gallagher to send captain Lewis Travis sprinting goalwards.
Hornets defender Ryan Porteous stopped him with a fine tackle but Hedges seized on the loose ball and, having juggled it on the top of a boot to get it under control, lashed high past Daniel Bachmann from a tight angle on the right.
“I’m delighted with the result and the performance,” said Rovers manager Jon Dahl Tomasson.
“We knew that coming to Watford with those quality players they have it could be difficult to dominate the game on the ball. We showed great organisation and discipline and I think we defended really well.
“We had five or six good moments in the first half where the quality of our passing and decision-making was not good.
“I was disappointed that we were not leading two or three-nil by half-time because there were some key moments. We spoke about those moments and in the second half we scored from one of those moments and could have scored a couple more.”
Matheus Martins, Watford’s Brazilian wideman, was the game’s outstanding individual and came closest to ending a Hornets league goal drought.
First he forced Rovers goalkeeper Aynsley Pears into a parry before smacking the crossbar before half-time. Later, after Hedges had fired Rovers in front, he saw Pears tip a goal-bound effort on to a post.
The win lifted Rovers up to ninth and left the Hornets stuck in 15th, without a goal in Championship action since the 43rd minute of their opening game.
“We missed making the goal to have that opener and the confidence and relief we needed,” Ismael added.
“We shot on the crossbar, we shot on the post, had dangerous situations and in my opinion we should have had a penalty as well.
“We tried to do the right things so my feeling is as long as we have the feeling that we are going the right way we have to stay calm and keep working hard.
“This is the Championship and we know that in two or three months it can look completely different. It is difficult to take that with their only chance of the second half the opponent wins the game.”