Alexandre Pato gifted Milan the lead after only 23 seconds of play before Pedro and David Villa turned things around. Nevertheless, a Thiago Silva header well into stoppage time meant that Barcelona had to settle for a 2-2 draw.
"Milan had very few chances. In fact, I reckon they scored from the only two they had: credit to them for being ready to take advantage when those opportunities arose," Victor Valdes was quoted as saying on Uefa.com.
"The key thing is to study the goals we let in and ensure they don't happen again. However, I think they were specific, isolated incidents, nothing more. When the scoreline is tight, like 2-1, these things can happen.
"And Milan have that champion mentality. You can never, ever write them off. Wherever they go, in whatever circumstance, they try to win. They are one of the great European sides and they already had our maximum respect."
Valdes then went on to express his disappointment with the final result and added that Barcelona have to learn from their mistakes.
"Football wasn't on our side. We've got a draw that leaves us very disappointed but we must lift ourselves as the competition has only just begun. Milan set themselves up very well out on the pitch and played in a direct manner in the second half. When the result is one which you don't expect, all you can do is to learn, especially if you have conceded from a set piece."
Barcelona's next match in Group H of the Champions League is the away game against BATE Borisov on September 28.
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