While defeat for Ireland's seniors in Switzerland tonight won't signal the end of Euro qualifying hopes, it's a different story for the U-21s earlier in Iceland (4.0pm).
The table-toppers will only have reached the campaign's halfway stage by full-time but their points tally will be crucial to qualification prospects.
Only the best runners-up across the nine groups join the victors in a direct route to the 2021 finals in Slovenia and Hungary. Otherwise, second clinches a play-off.
Italy, despite Stephen Kenny's side pushing them in last Thursday's scoreless draw at Tallaght, will fancy themselves to win the group. Their 1-0 win in Armenia last night cuts Ireland's lead to three points and the Azzurri have a game in hand.
For Ireland to realistically challenge the favourites heading into the business end of the campaign, six points are required from today and the visit to Armenia next month.
"Qualifying for the finals is the aim and I believe we have a great chance to do it," said Lee O'Connor, the 19-year-old full-back from Waterford, who moved to Celtic from Manchester United during the summer. "We had enough chances to beat Italy on Thursday. Like the manager said, we wouldn't have settled for a point beforehand. Now, instead of getting the six points we targeted from this double-header, it has to be four."
Iceland, with former Chelsea striker Eidur Gudjohnsen on their staff, have their own motivation, most pressingly a recovery from their 5-0 defeat to Sweden on Saturday. The customary necessary evil in these parts of an artificial pitch does offer the hosts a slight advantage, though it shouldn't diminish an Ireland attack carrying a powerful and pacey dimension.
Troy Parrott's suspension heightens the prospects of senior international Michael Obafemi clinching a first start at this level.
The Dublin-born Southampton striker impressed as substitute against the Italians, one burst from his own half illustrating his threat.
"Michael was running and dribbling 70 yards up the pitch with the ball; something not many players can do," noted Kenny, who will probably deploy the 19-year-old on the left side of his three-man attack.
Liam Scales performed well enough at left-back against Italy to retain his place, though another League of Ireland representative, Zack Elbouzedi, is facing competition from Gavin Kilkenny for a start.
Remaining fixtures - Today: Iceland (A). November 14: Armenia (A). November 19: Sweden (H).
IRELAND (Probable): C Kelleher (Liverpool); L O'Connor (Celtic), D O'Shea (West Brom), C Masterson (QPR), L Scales (UCD); J Molumby (Millwall), C Coventry (West Ham United); Z Elbouzedi (Waterford), C Ronan (DAC Dunajská Streda), M Obafemi (Southampton); A Idah (Norwich City).
Mick McCarthy has rounded on critics of an Irish side who, despite their fitful displays, culminating in Saturday’s dire 0-0 in Georgia, are 90 minutes away from securing an automatic Euro 2020 qualification berth.
After a build-up rich in positivity about the direction of Irish football, this was a reminder that there is nothing revolutionary about the attempts to qualify for Euro 2020.