Jurgen Klopp felt Liverpool "got carried away by our own football" as they let a lead slip against Milan before recovering to win 3-2 in their Champions League opener.
An own goal from Fikayo Tomori gave Liverpool the lead in the ninth minute at Anfield before Mohamed Salah saw a penalty saved by Mike Maignan.
Two goals in the space of 110 seconds turned the game on its head, however, with Ante Rebic and Brahim Diaz putting Milan, playing their first Champions League game since 2014, 2-1 up at half-time.
However, Salah atoned for his penalty miss three minutes after the restart and a superb long-range effort from Jordan Henderson, his first goal in the competition for 2,485 days, settled matters for Liverpool to send them top of Group B.
Klopp made four changes from the Premier League win over Leeds United, with Joe Gomez starting in defence and Divock Origi up front.
And he felt the alterations had an impact on Liverpool losing control of the match for a brief period.
He told BT Sport: "We started incredibly well. We played a super, super game. An intense game but football-wise as well. We played in all the spaces we had to play and didn't give them anything until... I'm not sure exactly. We got punished for it in the last few minutes of the first half but it started earlier.
"We got carried away by our own football. We didn't keep it simple anymore, offensively and defensively we were not organised anymore.
"When we are organised, Fabinho is incredible and he can pick up all the challenges we need him for. When the spaces are too big, even he cannot solve it anymore.
"They played in between and scored two goals. But it did not feel like we cannot come back. It was clear that we had to immediately get back to how we started and then we scored wonderful goals, to be honest. Both were incredible.
"It is deserved but we had 10 minutes where Milan nearly changed the whole tie.
"It is the football I want to see in most moments. We are experienced in the competition, or should be. It was a little bit the changes as well that we just weren't compact anymore.
"Now we won I can say that the changes was the right thing to do because playing every three days is just not possible with the same guys. The guys who came on did incredibly well.
"That is our pick from pot four. AC Milan in a really good moment. It is a tough group. That is why it is important we won this game. It does not decide anything but it gave us a winning start."