Petre Marin's penalty dashed hopes of a Motherwell comeback
Motherwell bowed out of the Europa League despite impressing in the second leg defeat by Steaua Bucharest.
Needing three goals to force extra-time, Jim Gannon's side pinned back the Romanians for long spells.
And Ross Forbes gave Well the lead in 17 minutes with a spectacular 20-yard volley from Paul Slane's corner.
But a rejuvenated Steaua dashed hopes of a Well comeback after the break through Petre Marin's penalty and Bogdan Stancu's double.
Jim Gannon's Motherwell side knew they needed to score an early goal to have any chance of overturning the 3-0 first-leg deficit.
And Forbes fired the hosts in front in spectacular style.
Slane's deep corner evaded everyone in the box, and Forbes lashed the ball past the helpless Rufay Zapata.
Steaua were struggling to deal with the aerial threat of John Sutton and the industry of O'Brien and Forbes.
With Motherwell goalkeeper John Ruddy a virtual spectator in the first half, the home side tried but were unable to add to their lead before the break.
Ross Forbes (centre) celebrates his stunning strike
Motherwell could have claimed a second goal 10 minutes before the break when Jamie Murphy's shot appeared to be handled by Sorin Ghionea, but the Spanish referee Carlos Gomez dismissed their penalty appeals.
Well should have doubled their lead after 41 minutes when Slane showed great skill to dance away from his marker before sending in a clever cross from the left-hand side, but Murphy failed to get his diving header on target.
Gannon's side were agonizingly close to doubling their lead just three minutes into the second half.
Sutton earned a foul after Ghionea shoved him in the back and, from the resulting free-kick, Forbes forced Zapata into a save.
The keeper's punch found Mark Reynolds and his shot fizzed just wide.
But Motherwell's good work was undone when Steaua scored with their first effort on target.
Stancu found himself free in the box after some neat passing down the left-hand side and the back-tracking O'Brien sent him sprawling in the box with a clumsy tackle.
Marin took the penalty and fired past Ruddy with a shot straight down the middle..
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