The Blaugrana were unhappy with the playing surface at San Siro, which cut up badly during the first-leg clash, and club officials aired their grievances during a post-game meeting with Uefa representative Mikalai Varabyov.
Milan, though, have now issued a public riposte on their official website in which they have claimed that Barca raised no concerns over the pitch after training at the venue on Tuesday evening.
"In reference to the official protest presented to Uefa by Barcelona regarding the condition of the San Siro pitch, AC Milan communicates that:
"1) The watering of the pitch, to be done within one hour before the game as agreed in the organisational meeting yesterday morning [Wednesday] and as per the regulations of the Uefa Champions League in section 14.15, was not carried out because of the conditions of high humidity on the pitch;
"2) The general condition of the pitch, on which Barcelona had trained the night before without raising any questions, was deemed suitable by both match officials and delegates from Uefa during the site visit yesterday morning."
Milan and Barcelona are set to meet in the second leg at Camp Nou next Tuesday.
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