Antonio Conte was saddened after violence marred the end of Chelsea's 2-1 defeat at West Ham.
Skirmishes broke out towards the end as police and stewards battled to maintain segregation behind the goal being defended by West Ham.
Conte had on Tuesday spoken positively of the atmosphere in English football and had hoped for the game to pass peacefully.
Conte, who was focused on the on-field action, said: "I must be honest, because I didn't see the situation. We were playing and I didn't see this.
"I don't like this type of situation. It's important to see always the right atmosphere.
"Above all in England, we are used to see the right atmosphere. This country is fantastic in this aspect.
"I'm sorry about this situation."
Chelsea had won three games in succession, scoring nine times without conceding, before West Ham brought the run to an abrupt halt.
Cheikhou Kouyate rose ahead of restored Chelsea captain John Terry to head the Hammers in front and Edimilson Fernandes struck a second three minutes after the interval.
The energetic and pacey Hammers exploited uncertainty in Chelsea's defence, with captain John Terry making his first appearance in more than six weeks following an ankle injury.
Terry was one of seven changes following Sunday's win over Manchester United, with academy products Nathaniel Chalobah and Ola Aina also starting.
Diego Costa and Eden Hazard were among those thrown into the action as Chelsea sought a comeback, but Gary Cahill's goal came too late for the visitors to try to seek an equaliser and force extra-time.
Conte said: "We didn't expect the second goal so early. This changed our plan. We tried to change the situation.
"I think that today we were a bit unlucky.
"It's a pity. When you lose, it's normal you see bad things. In this game I found a lot of positive things."