Shamrock Rovers manager Michael O'Neill admitted his side were punished for defensive lapses as Rubin Kazan inflicted their fifth successive defeat in Europa League Group A.
The League of Ireland side gave a good account of themselves in the first half and were perhaps unlucky to go in at the interval 2-1 down.
But further goals in the second half from Nelson Haedo Valdez - his second of the game - and Obafemi Martins made for an unflattering 4-1 defeat for O'Neill's side.
While they played their part in an entertaining contest, though, Rovers were culpable in defence - particularly for Valdez's double as the Paraguayan first seized on Ken Oman's error and then strolled clear of a shoddy offside trap.
"We were not surprised by Rubin's performance today," O'Neill said.
"We saw them in Dublin so we were aware of their ability.
"The disappointing thing was the nature of the goals we conceded, the first goal in particular. We made several mistakes, and of course such high-class players as Martins and Valdez took their chances and punished us for these mistakes.
"Generally our team reacted well. Up to the point when it was 2-1 to Rubin I thought the game was in the balance, but in the second half Rubin played especially well.
"There was definitely a lack of mental concentration. Generally, we were punished for bad decisions and poor defensive play."
Nevertheless, he had praise for his men after their improbable adventure on the continent - which briefly threatened to produce its greatest highlight after Oman atoned for his error by equalising within two minutes of Valdez's opener.
"This has been a historic season for Shamrock," he said.
"At this level of football, money is a big factor. Rubin have high-class players such as Martins, Valdez - they are very good, very fast and we can never afford players like them.
"I can't ask for more from my players - they did their best. We enjoyed our time in Kazan. Rubin is a top-class club. Everything was well organised. We will leave with fine memories."
Asked whether they will also leave with some of the local speciality vodka, though, he quipped: "No, we drunk it all here."
