David Jeffrey failed to get the result he craved in his final game as Linfield manager at Windsor Park.
An emotional Jeffrey applauded the fans as he walked to the dressing room for the last time after watching his team turn in a shocking performance.
Even though Cliftonville did what was required to retain the Danske Bank Premiership, this must rank as one of Linfield's poorest displays of the campaign.
Goals from young guns, Danny McKee and Jordan Stewart earned what was primarily a makeshift Glentoran side a 2-0 win; their first of the season against their Big Two rivals.
And even though is was an emotionally-charged occasion for the manager, his first thoughts were for his players.
"They didn't let me down, they let themselves down," said Jeffrey. "To be honest we got what we deserved – nothing.
"They have got to learn to perform in the big games. When you go out on to that pitch, there is no hiding place. We didn't do that. I couldn't point to any of my players and say that they played to anywhere near their full potential.
"We had a number of ex-players here. You always want them to see how the new group perform. Sadly they let themselves down. In fact, it cast a massive shadow on the progress they have made this year."
Jeffrey (pictured) has one more game in charge, a trip to Glenavon on Saturday, before he leaves Linfield after 17 years as manager.
"My time is now up, but I wish the new manager and the club every success in the future," said Jeffrey.
"We are leaving the club in a good position in which to build on. Last year we were something like 30 points behind Cliftonville. The secret is now building on what we've done and being more consistent."
Glentoran old boy Andy Waterworth created the first opportunity, by lobbing in a right wing cross, but Philip Lowry's header failed to trouble Elliott Morris.
Morris came to Glentoran's rescue early in the second half, getting down brilliantly to beat away a low Michael Carvill drive, after he was sent clear by a pin-point pass from Jamie Mulgrew.
The Glens silenced the home fans by forging into the lead on 59 minutes. Morris's long punt forward was picked up by McKee, who outpaced a static Blues defence before slotting the ball low past Tuffey.
Linfield attempted to repair the damage with substitute Ross Clarke dancing his way into the box, riding tackle after tackle before seeing his shot was superbly repelled by Morrris with his legs.
Glentoran finally killed the contest three minutes from the end when little Stewart, the smallest man on the pitch, met a super Fra McCaffrey flick to power home a header at the back post.
Linfield: Tuffey, Gault (McAllister 41 mins), Haughey, Callacher, Waterworth, Lowry, Carvill, BJ Burns (Garrett 70 mins), A Burns (Clarke 46 mins), Ward, Mulgrew. Subs: McVey, Thompson.
Glentoran: Morris, McKee, Hill, Henderson (Bradley 46 mins), McAlorum, Addis, McGuigan, Gordon, McCaffrey, Nelson (Stewart 70 mins), Scullion. Subs: Miskimmin, Hughes, Kerr.
Referee: A Hunter (Maguiresbridge).