Barca were already leading 3-1 against Celta Vigo when they were awarded the spot-kick, with Messi opting to pass sideways from the penalty spot for Luis Suarez to roll the ball in and complete his hat-trick.
Opinion has been divided over whether the Ballon d'Or winner's actions were the mark of genius or disrespectful to Celta, but Ancelotti believes the Argentine was completely within his rights to try the trick.
“I was really surprised,” he confessed to Goal. “It is a rule, and if you respect the rules, you can do what you want.
“If you do this in Spain, it’s OK, but if you do it in Italy, maybe you’ll have more problems. But if you respect the rules, everything is possible.”
“Maybe now Barca are better than Madrid, but you never know what will happen in March or April, when the competition is in the most important moment,” the veteran Italian coach explained. “You have to be ready in April for the quarter-finals and semi-finals, and May for the final.
“Madrid are competitive like Barcelona, like PSG, like Manchester City, who aren't doing that well at the moment but they have possibilities in the Champions League.”
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The ex-Chelsea and Madrid coach also stressed how difficult it is to retain the trophy, which no-one has achieved since Ancelotti was playing in Arrigo Sacchi's AC Milan team in 1989-90.
“Barcelona have a possibility to win it again because they have a fantastic squad, but you never know,” he said. “Maybe you are in fantastic condition now but in March or April you have some injuries and are not able to keep the same condition.
“They have the skills and the qualities to win the Champions League, but I’m not sure as no-one’s done it since Milan.”