Kilmarnock drop into the Conference League after their defeat in Belgium
Kilmarnock manager Derek McInnes lamented the mistake that knocked his side out of Europa League qualifying as they lost 1-0 to Cercle Bruges in Belgium and went down 2-1 on aggregate.
A blunder between Lewis Mayo and Liam Donnelly allowed Thibo Somers an easy first-half goal, with Kilmarnock now facing Tromso in the Conference League third qualifying round.
"I'm just so annoyed we lost the goal we lost," McInnes told BBC Scotland.
"One thing you can guarantee is that the ball will come into the box. They're not shy asking questions of you. We just needed to remain calm, a simple shout can deal with it.
"Their captain Somers is always in a goalscoring position, he always scores a lot of goals for them. It's all avoidable and that's why we're really annoyed."
Robby McCrorie denied Kevin Denkey from the penalty spot to swing momentum back to the visitors but they could not find a leveller and now drop down into the Conference League.
Norwegians Tromso overcame KuPS 2-0 on aggregate and will visit Rugby Park next Thursday. Cercle will play Norwegian side Molde in the next round of Europa League qualifying.
There was very nearly a perfect start for Killie as Kyle Vassell got in behind the hosts' defence early on and squared to Marley Watkins, but the Welshman fluffed his lines from just a few yards out.
Like with last week's game, this started in an open manner but soon became quite one-sided as Cercle came forward in waves of attack.
The opening goal was of Kilmarnock's making, though. A simple cross from the right was not dealt with by Mayo and Donnelly, with the ball dropping kindly to Cercle skipper Somers to sweep home.
They were almost gifted a second on the brink of half-time when McCrorie punched a corner straight to Hannes van der Brugge and the midfielder headed a few inches over the bar.
Cercle's best chance to put the tie to bed came from the penalty spot when Vassell was penalised for a handball after a VAR intervention.
Star striker Denkey stuttered in his run-up and sent a tame penalty to McCrorie's right, and the Killie keeper went the right way to smother the ball.
That gave the visitors some momentum and they enjoyed 10 minutes of pressure on the Cercle goal, but they could not force home an equaliser, despite chances for Stuart Findlay and Watkins.
Player of the Match - Thibo Somers (Cercle Bruges)
The Cercle captain was at the heart of anything good they did offensively
Missed opportunity for below-par Kilmarnock - analysis
It was a disappointing first-half showing from Kilmarnock, far from what they showed last week.
There was little composure on the ball - which led to little time on the ball - and little composure off it. The Cercle goal was entirely preventable and there were a few more chances that Kilmarnock offered up freely.
However, the hosts failed to properly punish Kilmarnock and there was a spell in the second half where it seemed the visitors would force a goal.
But there was no composure in the box, either. Findlay and Watkins both fluffed chances in the second half that should have rippled the net and when those chances were not converted, the hope diminished.
What they said
Kilmarnock 'just not there yet' - Derek McInnes
Kilmarnock manager Derek McInnes: "We were just lacking a wee bit of quality and at this level, there's no shame in saying we're not quite there yet. But it was a tight game, similar to Rugby Park.
"The only surprise is the type of goal we lost. We're normally very good at defending the middle of our goal but it's cost us tonight. It's no fault of the players' effort."
What's next?
Kilmarnock visit reigning champions Celtic in their Scottish Premiership opener on Sunday (16:30 BST).
