David Moyes apologised for losing his cool with a ball boy after he was sent off as West Ham missed out on a place in the Europa League final.
Manager Moyes was ordered to the stands late on for kicking a ball thrown by the ball boy as West Ham lost 1-0 on the night to Eintracht Frankfurt and 3-1 on aggregate.
"I kicked a ball back at the ballboy, so I apologise for that, he threw the ball very softly at me," Moyes said on BT Sport.
Television footage of the incident showed an angry Moyes lashing out.
Moyes' team were forced to play most of the match with a numerical disadvantage after Aaron Cresswell's 18th-minute sending off made him the first Englishman to receive a red card in a European semi-final since John Terry for Chelsea against Barcelona in the 2011-12 Champions League.
According to Moyes, West Ham have faced better teams than Oliver Glasner's Frankfurt on their European run, but Rafael Borre's first-half goal condemned the Premier League side to a semi-final exit.
Cresswell also became the first English player to be dismissed twice in the same edition of a major European competition, having also seen red in a quarter-final draw against Lyon.
While Moyes said sorry for his own actions, he was unhappy with the decision to dismiss Cresswell, and suggested West Ham's previous knockout opponents Lyon and Sevilla were stronger than Frankfurt.
"[We have] lots of complaints," Moyes told BT Sport after the defeat. "We've enjoyed being in the competition. I don't know if we've enjoyed the officiating, but we have enjoyed the competition. I just feel disappointment, because I think this was a chance. I think we probably played better teams than Frankfurt.
"To be honest, we probably lost the game in the first 30 seconds at the London Stadium, where we conceded a goal [scored by Ansgar Knauff] and we've been chasing the game ever since."
He added, on West Ham TV: "We had a sending-off tonight and I think over the two games, for some reason, a lot of things haven't gone our way.
"But maybe we have to learn a little bit more about officiating in Europe and different things. We've now had two sendings-off in games – one in the quarter-final as well, when we had to play 45 minutes with 10 men.
"Tonight, we had to play the best part of 75 minutes with 10, so the players are brilliant. How they've worked and their resilience to keep going… and actually, I thought they tried to take the game to Frankfurt and had chances."
West Ham travel to relegated Norwich City in the Premier League on Sunday as they aim to secure a top-seven finish.
While West Ham missed the opportunity to reach a first major European final since they lost to Anderlecht in the 1975-76 Cup Winners' Cup trophy match, Frankfurt have now reached their third such occasion, having been European Cup runners-up in 1959-60 and UEFA Cup winners in 1979-80.
Glasner's men will face Rangers in the final in Seville later this month after the Scottish outfit overcame RB Leipzig 3-2 on aggregate.