Aberdeen face an uphill task to progress in the Europa League after losing 2-0 in Rijeka.
Second-half goals from Antonio-Mirko Colak, a penalty, and Robert Muric undid good defensive work from the Scottish Premiership side in their third qualifying round tie.
Aberdeen – who had won 3-0 at Rijeka in the second qualifying round four years ago – created few chances on a cagey night in Croatia.
But Rijeka attacks were also largely blunted until Shay Logan grabbed Colak's shirt after 61 minutes when there appeared little danger.
Muric further tilted the tie Rijeka's way two minutes from time with a splendid low shot from 20 yards.
Scott McKenna lined up at the heart of the Aberdeen defence despite being unsettled at Pittodrie.
McKenna had handed in a transfer request earlier this week amid interest from Nottingham Forest, QPR and Sheffield Wednesday, but the Scotland international was unfazed as he and his centre-back partner Andrew Considine kept the hosts at bay.
There was a new face on the Aberdeen bench as Zak Vyner had flown to Croatia after completing a season-long loan from Bristol City.
Aberdeen were content to defend deep in the first half and look to break quickly, although in truth there was little for Rijeka to be concerned about.
Sam Cosgrove offered a threat at set-pieces, but he rarely looked like adding to his six-goal tally in the Europa League this season.
Rijeka were restricted to speculative efforts – Colak and Tibor Halilovic both tried their luck from distance – before Joe Lewis was called upon for the first time on the half-hour mark.
Aberdeen were caught napping at a corner and goalkeeper Lewis made a superb point-blank save from Ivan Lepinjica, with Dario Zuparic sending the rebound wide from eight yards.
Halilovic fired wide after the re-start and Aberdeen, who had slowly began to play further up the pitch, were punished when Logan grabbed Colak and the striker got off the turf to coolly dispatch the penalty.
Aberdeen came close to an equaliser when Considine touched on Niall McGinn's free-kick close to the penalty spot.
But the ball fell agonisingly the wrong side of the post from an Aberdeen point of view, and Rijeka doubled their lead two minutes from time.
Muric found a yard of space and superbly curled the ball around McKenna and into the bottom corner of the net, giving Lewis no chance.
It was a crushing blow for Derek McInnes' men and leaves Aberdeen with it all to do in the return leg at Pittodrie next week.
No Data Analysis info
