An understrength Glentoran were outclassed by League of Ireland champions Sligo Rovers at the Showgrounds on Monday night.
Showing six changes to the starting team that beat Knockbreda in the Irish Cup on Saturday, Glentoran were put to the sword early on against the north-western full-timers.
Without Sean Ward, Mark Clarke, Jay Magee and Stephen Carson, while Andrew Waterworth and Richard Clarke started on the bench.
For their part, Rovers were without the injured Danny Ventre, Seamus Conneely and Danny North and new signing Kieran Djilali was only introduced to fans at the half-time break.
But such was their strength in depth that they home side had the ball in the net after just 130 seconds, with Lynch superbly volleying debutant Anthony Elding’s knockdown to the net from inside the area.
Elding had an effort ruled out for offside shortly after, but got the goal his play deserved when heading home Lynch’s cross from close range on 20 minutes.
Before that, the best Glentoran offered was a counter attack led by Carl McComb on the right, but he lost his footing on the sandy pitch under pressure from Ross Gaynor.
In truth the part-time visitors looked tired and spent most of the evening chasing shadows. And they were unable to keep up with the intelligent running of David Cawley, who broke down the right on 37 minutes before picking out Ryan Connolly to flick home Rovers’ third.
Connolly’s cross from the left then rebounded kindly for Lynch to fire his second, and the hosts were four clear by the break.
They did not let up in the second half, with Evan McMillan heading home Joseph Ndo’s cross on 53 minutes, and Cawley denied an audacious backheel goal by Glentoran keeper Elliot Morris.
The introduction of Waterworth, Clarke and Daniel Burns breathed a bit of life into the Glentoran challenge.
Alan Keane had to revert to some desperate defending to prevent Carl McComb’s cross causing trouble.
The resultant corner was flicked goalwards by captain Colin Nixon, but rose too high.
Nixon was doing his utmost to try and at least give the travelling Glentoran fans, who numbered about 200, something to shout about before the full-time whistle.
He say another late effort smothered by goalkeeper Gary Rogers, as Glentoran enjoyed their best spell of the game in the closing stages.
They could not find a way through, however, and now face an uphill task to advance to the semi-finals in next Monday’s second leg.
Sligo: Rogers, Keane, McMillan, Peers, Gaynor, Ndo (Millien 62), Lynch, Cawley, Connolly, Greene (Martin 74), Elding (Cretaro 62).
Glentoran: Morris, Nixon, Birney, Bradley, Hill, Callacher (R Clarke 68), McAlorum, McGuigan, O’Hanlon, Murray (Burns 77), McComb (Waterworth 58).
Ref: R Crangle.