However, they needed one more goal to go above Arsenal in the group and as such had to settle for a place in the Europa League owing to an inferior goal difference to Borussia Dortmund and the Gunners.
"It cannot be anything else but bad luck, because to win four games out of six and be eliminated is not something that happens often," he told UEFA.com.
"Not going through is incredible. It is an injustice, really. Going out with 12 points - winning four games in such an immensely difficult group with two sides as strong as Arsenal and Dortmund - when you see teams going through with only one or two wins, with six or seven points, it's disappointing. We've got to look forward though.
"There was a stage in the game when we were tired - we'd put in a great deal of effort, but now we've got to look forward to the Europa League, Serie A and the Coppa Italia. Our aim now is to win the Europa League. It's a trophy and it is very important for us."
In Group G, Zenit St Petersburg finished second with just six points.