Messi admits he is still haunted by the penalty he missed in the UEFA Champions League semi-final against Chelsea last season, when Barcelona failed to press home their numerical advantage following John Terry's red card in the second leg.
"I felt terrible," he said. "Angry at myself because I knew that at that moment the whole tie was in my hands, but I can't do anything about it now.
"It's past but it was a very tough moment for me and I still think about it."