Fonte also claimed that he understood why the West Ham supporters gave the team such a disgruntled response come the final whistle, acknowledging that the result was not pleasant.
"We need to look at ourselves in the mirror," the defender told Sky Sports News. "This happened a few times last season. We have to put this right. We are West Ham and it's just not possible.
"It's disappointing. It's a night to look at and learn from. I won't say it's unacceptable. The players tried hard. We tried the best we could, but sometimes it doesn't go your way.
"How can we not understand [fans booing]? They don't like to lose 3-0 at home. We don't either. We're all frustrated, we apologise and we work hard on the training pitch.
"It's not only the manager, it's the players as well. We have an unbelievable squad and should not be in this position."
The result sees West Ham slip to 17th in the Premier League table, two points above the relegation zone.