Aberdeen lost 2-0 in Rijeka to leave them an uphill battle to progress in Europa League qualifying.
After the sides went in for half-time goalless in the third qualifying round first leg, a penalty conceded by Shay Logan and converted by the fouled Antonio Colak, and then a strike from Robert Muric, put the Croatians in pole position to qualify to meet either Gent or AEK Larnaca in the play-offs.
The sides meet again at Pittodrie next week.
Scott McKenna retained his place in Derek McInnes’ starting line-up, despite the centre-back submitting a transfer request ahead of the Premiership win over Hearts following bids from the English Championship.
Both sides felt each other out in the opening 25 minutes, with Rijeka able to retain possession for longer periods without doing much with it.
Tibor Halilovic’s shot was the home team’s best early effort, but Reds skipper Joe Lewis watched it fly over the bar.
However, on 30 minutes, a corner bounced into the Dons box and Ivan Lepinjinca forced Lewis to block his low effort at point-blank. Dario Zuparic then hit wide on the rebound.
McInnes’ men were struggling to hold on to the ball when they won it back, but they saw out the half.
After the break, Aberdeen started well, with right-back Logan sending Niall McGinn down the right flank and the winger delivering a ball into the box for Sam Cosgrove.
But, on 51 minutes, Halilovic could’ve opened the scoring when he flashed a 18-yard shot just by Lewis’s left upright.
On 60 minutes, the visitors blinked. Shay Logan pulled the shirt of Luka Capan, who fell dramatically in the box, and the referee, Ricardo De Burgos Bengochea, awarded a penalty.
Antonio Colak smashed the penalty low to Lewis’ right and, despite the keeper going the right way, the ball found the net.
Even though they’d taken a hammer blow, Aberdeen could’ve scored a couple of minutes later, when McGinn’s cross from the left went through everybody and just missed both Andy Considine’s boot and the far corner of Rijeka’s goal.
McInnes threw on Scott Wright and Dean Campbell, for McGinn and Jon Gallagher, as well as Curtis Main for Ryan Hedges, in an attempt to shore up the midfield and add more of a physical presence to nick an away goal.
However, it was the Dons who conceded again – two minutes from time and leaving them a difficult task at Pittodrie – Robert Muric sidestepping Dean Campbell and firing left-footed into Lewis’ bottom left corner from the edge of the area.