Watford boss Vladimir Ivic says captain Troy Deeney sat out their 2-0 Championship defeat to Huddersfield due to a "discipline issue".
The Hornets striker was an unused substitute in this sorry performance in West Yorkshire.
His omission was puzzling considering he had scored in his three previous outings.
When quizzed on Deeney's no-show, Ivic said: "He didn't start because he played a lot of full games recently.
"I believe that he wasn't ready to play from the beginning but the reason he wasn't able to come on was a discipline issue."
When asked if Deeney had a future at the club, Ivic added: "I don't know, we will see.
"It's between us and I don't want to speak about this. I'm the coach and I know what is my responsibility."
The hosts took an early lead when Campbell slotted into an empty net after just nine minutes.
Veteran goalkeeper Foster took far too long with a backpass and his attempted clearance was charged down by Isaac Mbenza and into the path of Campbell just a few yards out.
Watford rallied but saw home keeper Ryan Schofield pull off a fine reaction save to deny James Garner from just a couple of yards out.
Further pressure from the visitors amounted to little before the hosts doubled their advantage after 32 minutes.
Mbenza was again involved, this time when his inswinging corner was inexplicably sliced into his own net by the hapless Capoue.
Watford upped the ante after the restart but the decision to keep Deeney on the bench all afternoon seemed a particularly puzzling one given the Hornets' struggles in front of goal.
Andre Gray hardly had a sniff and when he did he came up against an alert Schofield.
Watford have now dropped down to fifth in the Championship and Ivic added: "We had problems right from the beginning.
"We made mistakes early on and we paid for these two mistakes with the two goals Huddersfield scored.
"We created more in the second half and were more dominant but as I say our problems started from the first minute.
"We created some chances but were without any ideas and confidence in the first half. We need to do much better."
Town had few chances to add to their tally after the interval but the damage was done in that first half.
Their two-goal buffer ultimately proved more than enough as they moved to within five points of an unlikely play-off spot.
This was also a fourth home win in succession for the Terriers – the first time they have achieved such a feat since February 2017.
Head coach Carlos Corberan said: "We knew the level of quality that Watford have and I was expecting a tough game but our effort and commitment was amazing.
"It's hard to find one player that didn't play with the correct enthusiasm and desire.
"Ryan Schofield played well but for me to individualise just one player would not be fair as I cannot say that Campbell or (Lewis) O'Brien were less important, for instance.
"The merit of this positive results we are getting is for the players."