A first-half goal from Wout Weghorst sent Dundalk to a 1-0 Europa League defeat at home to AZ Alkmaar.
Weghorst struck the only goal with nine minutes on the clock, but Dundalk remain in with a chance of qualification.
If they beat Maccabi Tel Aviv in their final group game and AZ do not beat Zenit, they will progress.
On a biting cold night at Tallaght Stadium, much-tested goalkeeper Gary Rogers was Dundalk's stand-out performer.
He was first called upon five minutes in and again moments later during a scramble in the box which finally led to AZ taking the early lead.
An eighth-minute corner was cleared before a second attempt from the flag moments later caused chaos in the Dundalk defence.
The ball came off the foot of the Lilywhites' Dane Massey and straight into the firing line of Weghorst, who tapped it confidently into the net.
Undeterred, the Irish underdogs launched a sustained assault on the visitors' goal for much of the remainder of the first half.
In their most convincing period of the game, a great chance on the half-hour saw Ronan Finn put the ball into box to threaten an equaliser but his cross was eventually forced for a corner.
Daryl Horgan's lob back into the danger zone was headed over the crossbar by Ciaran Kilduff.
Ten minutes later midfielder Stephen O'Donnell, who has been beset by hamstring and calf injuries, pulled up after leading a charge.
In the first substitution of the game he was replaced by John Mountney.
There were few more chances for Dundalk in an often scrappy second half.
Rogers was called upon several times to stop AZ doubling their advantage, not least in the 58th minute when his diving save blocked Weghorst.
Horgan threatened at times but squandered a great opportunity when he fired the ball straight at the keeper, as well as a meekly taken free kick deep inside AZ's half which also came to nothing.
Kilduff came off in the 76th minute to a standing ovation, replaced by Davis McMillan and that was quickly followed by a second change with Dean Shiels coming on for Patrick McEleney.
But it was too little, too late.
A goal-bound 83rd-minute effort from Sean Gannon took a deflection and went wide, leaving Dundalk with an uphill struggle to make it into the last-32.