Atletico Madrid captain Gabi has said the travelling support spurred the team on to victory over Milan.
Los Colchoneros won 1-0 through a late Diego Costa goal to claim an away win with the return at Vicente Calderon to come next month.
Gabi was pleased with the performance and put it down to the large number of Atleti fans who made the journey to Italy.
“We played a very serious game and we’re very happy,” the midfielder told reporters after the match.
“3000 fans spent their money to come here and we had to give everything for them.”