The former Arsenal man had nothing but praise for Barca's performance after Tuesday evening's thrashing at Camp Nou
The Serie A representatives were optimistic about their chances of reaching the quarter-finals of the competition after their 2-0 first-leg win, but they were unable to hold off Barca in the return, and Flamini was thoroughly impressed with the Blaugrana's performance.
"I think Barcelona played a great game. They played unbelievable football, with very quick passing," Flamini told Uefa.com.
"It's true that we had the opportunity to score in the first half when [M'Baye] Niang hit the post but we didn't take it and if you don't score when you have such a chance then things become very difficult.
"There's not much more to say – Barca played great. Of course, we knew this was a big team and that they play quick passing, quick football and today they produced the better game. We didn't really play well.
"We had problems to get out of defence, everything went well for them and we couldn't get that goal which might have changed things."
It is the second year in succession that Milan are eliminated from the Champions League by Barcelona after they stumbled in the quarter-finals last term.