The Giallorossi were leading away to Panathinaikos before conceding twice in the final minutes for a 3-2 defeat. At the Olimpico they had again gone in front, but let in three in five minutes on the stroke of half-time to lose by the same result.
Ranieri lamented: "We had four minutes of insanity in Athens and four here. We should've dealt better with the lead, as in international football you cannot afford these mistakes. Panathinaikos were within our reach and we played well, but have to accept the result. It's a shame for the fans."
Only this week Ranieri had said the Europa League was his main target for this season, despite closing in on Serie A leaders Inter.
"We wanted to do well, the stadium was packed and the atmosphere wonderful, but it's incredible how we threw it away. Already when it was 1-0 we weren't neat enough. We handed them the penalty and the shot for their second goal. The game was in our hands and we let it slip.
"During the half-time break we talked about remaining united as a squad so we could leave the field with our heads held high. The team pushed, but eventually the absence of David Pizarro, Francesco Totti and Luca Toni took its toll.