Shamrock Rovers manager Stephen Bradley has challenged his players to learn from last week's below par Champions League performance as they take on Breidablik in the Kópavogsvöllur Stadium.
The Hoops are a goal down after Damir Muminovic's thunderous free-kick proved the difference between the teams last week.
It could have been worse on a night when Rovers goalkeeper Leon Pohls was called into action on several occasions.
A spell of openings early in the second half was the best the Hoops had to offer and brought hope.
A chance for Sean Kavanagh was their best on the night, while a tame effort by Johnny Kenny and Graham Burke being denied by Viktor Karl Einarsson were the highlights.
The first leg ended 1-0, far from insurmountable, but it was the nature of the defeat - outplayed at home - which gave cause for concern.
Bradley said he took responsibility for "the information and how it was given" to his players, saying he felt they gave the opposition too much respect in the opening 45 minutes.
He was adamant after the second half in Tallaght that "if we play at that level I have no doubt in my mind we can win the game and go through".
That remains to be seen and it leaves the tie extremely well-poised on the home turf of the Icelandic champions who impressed many observers.
Viktor Einarsson was sensational for Breidablik while Jason Dadi Svanthorsson was also a threat throughout.
Two of the most creative players for the Hoops will miss this game.
Jack Byrne made a surprise return for the game last Thursday after overcoming a knee issue.
However, it has been confirmed Byrne suffered an injury and is now unavailable once more.
Neil Farrugia is also absent with Bradley saying he has "had a little setback". Trevor Clarke has a few more weeks to sit out.
Defeat in this would be a major setback for the Tallaght outfit.
They would drop to the second round of the Europa Conference League and need to come through three rounds to reach the group stage, starting with the loser of KÍ Klaksvík (Faroe Islands) v Ferencváros (Hungary). That first leg was 0-0 last week.
Bradley said: "We work so hard every day and every week to play in Europe and play in big games. We definitely want more of them and obviously, that’s the reward, more big games and we’ll do everything on Tuesday to make sure that happens.
"We’ve just got to reach our levels. We know we can do that and we’ve shown over the years that we can win home or away. We need to learn from Tuesday, especially the first half, and put that right.
"We were obviously frustrated because we felt that for large parts of the first half, we allowed them to play their type of game, and that was frustrating afterwards but sometimes it happens in Europe. You learn from it and make sure we’re ready for a different type of game on Tuesday."
Follow a live blog on Breidablik v Shamrock Rovers on RTÉ.ie/Sport or the RTÉ News app from 8pm on Tuesday
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