Steve Clarke lamented a slow start against Fulham and the dismissal of Peter Odemwingie, who vowed to learn from his mistake.
West Bromwich Albion went down 3-0 at Craven Cottage on Saturday as Dimitar Berbatov struck twice on his home debut and Steve Sidwell added a late third.
Odemwingie was shown a straight red card in the 38th minute, when Fulham were just one ahead, and Clarke admitted it had been a tough day at the office.
"It is obviously disappointing. We started the game slowly and I was disappointed with that. We allowed Fulham to control the game," the Baggies boss told Sky Sports.
"We deservedly went a goal down and the sending-off of Peter compounded the problems we had and made for a long afternoon."
Clarke refused to be too critical of Odemwingie, saying: "We are all human, everybody has got emotions.
"He thought he had a free-kick against him, the red mist obviously came down and he will take his punishment.
"He will get his three-game ban and the club have got a disciplinary process we will go through, and we move on. In football it happens, people get sent off."
Odemwingie admits that he let himself and the team down after kicking out wildly at Sascha Riether.
While the incident was out of character, he still recognises that he must take lessons from what happened to make sure it remains a one-off.
He explained: "Now I have time to think about the whole scenario and what really happened. I felt a good kick on my ankle, maybe from the back, and the linesman wasn't far.
"Nobody noticed it and I felt a bit of injustice, so I lost my temper at that moment.
"It is not my habit. It has happened once in a while in ten years. If I keep doing that there is a problem, but of course I am disappointed and I will learn from that.
"In an important game, maybe at the end of the season, if I am in a similar situation I will make sure I do not make a repeat of it."