Bray Wanderers reignited the race for fourth spot with this emphatic win at Maginn Park.
The heavy loss for Kenny Shiels' side was their fourth in a row, as Wanderers' quick countering play ensured they cruised to a deserved win.
City went close to breaking the deadlock on 14 minutes after Ronan Curtis did well to win possession before picking out Rory Patterson, but his shot was blocked by Bray skipper Conor Kenna.
Seven minutes later Wanderers took the lead as Aaron Greene latched onto Gary McCabe's pass before showing super composure to lift the ball over City keeper Gerard Doherty.
Wanderers keeper Peter Cherrie had to make a smart save on 30 minutes to keep out Aaron Barry's close range strike, but after that Harry Kenny's side netted twice in quick succession to end the game as a contest.
Firstly, on 35 minutes Noonan was on hand to side-foot the ball home, after Greene's initial clever pass gave Doherty no chance.
Then, two minutes later and with their tails up, Ryan Brennan ghosted through the City back-line before firing high into the net.
Early in the second half, Cherrie had to make a super finger tip save to keep out Patterson's close-range strike but Wanderers incredibly added a fourth on 56 minutes as Brennan's initial strike came back off the post before McCabe blasted home the loose ball.
On 79 minutes, Greene again showed great pace to get away from the City defence before beating past a frustrated Doherty.
In the closing stages, Derry's miserable night was summed up as Aaron McEneff saw his penalty sail well over, after substitute Lukas Schubert was brought down inside the box.
Derry City: G Doherty, McDermott, Toal, Barry, B Doherty; McEneff, Low, McNamee; McIntyre (Schubert 69), Patterson, Curtis (Dolny 56).
Bray Wanderers: Cherrie, Sullivan, Kenna (Douglas 65), Buckley, Brennan, Greene (Pender 82), Moore, McCabe, Clancy, Noone, Marks.
Referee: Neil Doyle (Dublin)