Defending champions Sligo Rovers moved to within four points of St Patrick's Athletic as they edged above Derry City with this fine away win that continues their impressive record over the Candystripes.
David Cawley and Danny North netted the goals for the Bit O' Red tonight, Cawley steering home in style in the 65th minute before the clincher was added by substitute North eight minutes from the end, ensuring Ian Baraclough's men held sway even when Derry sub Sean Houston made for a nervous finish with an 88th minute strike.
Sligo also owe a debt of gratitude to their goalkeeper Gary Rogers, who was excellent. Rogers pulled off some excellent saves to keep City at bay - not least from a golden City chance in the 53rd minute when he saved a Rory Patterson penalty.
Ref' Anthony Buttimer awarded the home side the spot kick when he deemed Patterson to have been fouled by Gavin Peers. Patterson assumed responsibility, but watched in horror as Rogers not only guessed correctly but also got a strong hand to turn his effort away for a corner. Patterson was on the end of the corner, but a dipping effort was well tipped over by the agile Rogers.
As if that wasn't bad enough for the boisterous Brandywell, Sligo took the lead twelve minutes later. Kieran Djilali, Seamus Conneely and David McMillan all had their roles in an intricate series of passes that culminated when Cawley grabbed possession and drove a precise, angled drive into the far corner past Gerard Doherty.
Sligo's second was netted when North raced to a through ball, nipping in ahead of Shane McEleney to drive past Doherty and stun the Brandywell.
City were given a lifeline when Houston powered high into the net two minutes from the end, but it wasn't enough to inspire a comeback.
It will have been a painful defeat for Declan Devine, who had called on his side to reverse a horrid sequence of results against their North-West rivals.
Derry have not now beaten Sligo in four years - their last win coming four years ago, in a 4-0 win at the Showgrounds in August 2009 - with Sligo now unbeaten in ten games against Derry. Indeed, you have to go all the way back to July 2007 for Derry's last success over Sligo at the Brandywell.
Devine knew what this meant and had written in his programme notes: "I feel we owe Sligo one as they have been getting the better of us over recent seasons and, obviously, we'd like to put that right."
The champions had opened brightly and took the game to Derry early on. Their intent was clear when Djilali burst through only to fire over with just 80 seconds on the stopwatch. Before the two-minute marker had arrived, there had been time for McMillan to win a corner off Shane McEleney.
Sligo were on top and Doherty was sprung into action in the sixth minute, the Derry stopper equal to Cawley's effort.
City threatened only briefly in these moments with Patrick McEleney driving off target before a free kick from the returned Patterson found a way through but fizzed just wide. Devine has consistently reminded us of the importance of the squad - and the City boss made four changes to his side from that which had begun in Thomond Park on Sunday.
Barry McNamee was named in the Republic of Ireland U21 squad earlier in the week, but he was one of four to make way, with Michael Duffy and Michael Rafter joining the injured Kevin Deery in missing out.
Top scorer Patterson was back and he was joined up top by the in-form David McDaid, while there were also returns for Shane McEleney and Barry Molloy.
Derry settled into it and a neat passage might have broken the deadlock in the 19th minute, but McDaid shot across Gary Rogers and narrowly wide after being played in by McEleney.
Sligo ought to have hit the front on the half-hour mark when Joseph Ndo gently slipped through the home defence for McMillan, but he slid past Doherty and wide when one-on-one with the City 'keeper with the best chance of the first period.
Simon Madden has been a key component of Derry's attack this season - and the full-back had Sligo hearts in mouths with a couple of dangerous crosses. First, in the 35th minute, Madden latched onto a magnificent cross-field pass by Patrick McEleney, with his subsequent cross punched away for a corner by Rogers. A free-kick routine from the hosts saw Madden power in a cross that forced Alan Keane to head clear from beneath the bar.
Both teams had half chances early in the second half, with Evan McMillan seeing an acrobatic effort trickle wide while a downward Ruaidhri Higgins header was dealt with by the Sligo rearguard.
After falling behind, City set about salvaging the tie and on the hour, showed their worth with a sweeping move involving Paddy Kavanagh and McDaid that ended with Kavanagh's low cross being fired just over by McDaid when he really should have hit the target. Cawley tried his luck for a second, but was denied by Doherty.
At the other end, Rogers had been the bane of much of City's night and, just after their second, he saved brilliantly from Madden's magnificent volley. Rogers was breached by Houston, just after his introduction, but Sligo held firm. In a title race where ever inch will count, this could be a big result for the champions. Just five points are between the top four now.
Fasten the seat-belts.
Derry City: Ger Doherty; Simon Madden, Ryan McBride (Sean Houston 79), Shane McEleney, Eoghan Osbourne; Patrick Kavanagh (Michael Duffy 85), Ruaidhri Higgins, Barry Molloy, Patrick McEleney (Mark Griffin 90); Rory Patterson, David McDaid.
Subs not used: Michael Rafter, Ryan Curran, Barry McNamee, Eugene Ferry.
Booked: Kavanagh (22), S McEleney (67).
Sligo Rovers: Gary Rogers; Alan Keane, Gavin Peers, Evan McMillan, Iarfhlaith Davoren (Jeff Henderson 78); Seamus Conneely, Joseph Ndo, Lee Lynch, Rafael Cretaro; Kieran Djilali, David McMillan (Danny North 68).
Subs not used: Anthony Elding, Pascal Millien, Lee Lynch, Ciaran Kelly, Liam Martin.
Booked: Ndo (23), Cretaro (52).
Referee: Anthony Buttimer.
Attendance: 2,500 (estimate).
Extratime.ie Man of the Match: Gary Rogers (Sligo Rovers).