Glentoran's Setanta Cup hopes are almost certainly over after they were hammered 3-0 at home by Shelbourne.
Jason Byrne's deflected free-kick puts Shels into the lead
Jason Byrne's deflected free-kick deceived Elliott Morris in the 17th minute and Morris was caught off his line by Ollie Cahill's 30th minute lob.
Sean Holmes clipped the Shels bar after half-time but Byrne's 68th minute goal wrapped matters up for the Dublin side.
Mathematically, the Glens can still qualify but they need a 5-0 win over Linfield and hope Shels beat Derry.
Shelbourne dominated the contest right from the start and both Cahill and Byrne had close-range efforts blocked in the opening five minutes.
The superb former Cameroon international Joseph Ndo then produced a sensational run through the heart of the Glens defence in the 12th minute but Mannus averted the danger by bravely diving at the Shelbourne man's feet.
However, Morris was caught badly flat-footed in the 17th minute when Byrne's less than powerful free-kick seemed to take an age to go in after being deflected.
Byrne and Glenn Crowe missed further chances to add to Shelbourne's lead before Cahill's delightful lob over Morris from 30 yards added to the the visitors' lead on the half hour.
Glentoran did improve after the break with Gary Browne having a cross-shot blocked by goalkeeper Steve Williams and Michael Halliday lofting an effort just over the bar.
However, Shelbourne quickly regained the initiative and Crowe had two chances saved by Morris while Byrne miskicked in front of goal after he had been presented with a glorious chance.
Ndo then produced another sensational run through the Glentoran defence but bizarrely opted to try and find a colleague instead of going for goal himself.
Holmes clipped the Shelbourne crossbar in the 62nd minute but the contest was over when Byrne struck the third goal in the 68th minute after a clever pass from Bobby Ryan.
Shelbourne move to eight points in the table but still need a point in their final group game against Derry next Monday to be certain of making the semi-finals.
Glentoran manager Paul Millar acknowledged that Shels had fully deserved their victory.
"They were by far the better side and wanted it more than we did," said Millar.