Ten-man Sligo Rovers held on for a point at the Brandywell to put a further dent in Derry City’s title hopes.
The Candystripes have now taken just two points from a possible six over the weekend and remain two points behind Shelbourne with just three games remaining.
Ruaidhri Higgins’ team were again lacking urgency in the first-half and they paid the price for that by falling behind on 34 minutes.
The Brandywell was absolutely stunned by a spectacular effort from Connor Malley, who volleyed an unstoppable strike beyond Brian Maher from close to 30 yards out to give the visitors the lead.
The game had barely kicked off again when City suffered again with the loss of Pat Hoban to injury, with the League’s top scorer replaced by Danny Mullen.
Sligo were completely on top in the opening stages of the second-half, and just when the Derry fans were losing faith completely, their team was gifted an equaliser.
Mullen sent Paul McMullan racing down the right, and his cross was headed into the arms of Ed McGinty until defender Reece Hutchinson sliced the ball over his goalkeeper’s head and into the net to make it 1-1 completely against the run of play.
Derry should then have taken the lead when a sensational turn by Whelan ended in a chance for McMullan, who seemed to do everything right as he jinked his way through the Sligo defence to create a shooting chance, but his effort somehow stayed out, McGinty saving before the rebound deflected off Niall Morahan and wide for a corner.
A dramatic second-half took another turn with just 15 minutes remaining when Sligo were reduced to 10 men after Luke Pearce received a second yellow card for a late challenge on Maher.
Despite that, Sligo remained a threat, and with defending thrown out the window in the last 10 minutes, they could have scored again when Simon Power set up William Fitzgerald in the area, but he shot well off target.
Derry pushed for a late winner and almost had it on 90 minutes when Duffy’s free-kick found Whelan at the back post, but his header was pushed behind by McGinty.
Derry City: Maher, Boyce, Connolly, Wisdom (Whelan 46), Coll, Diallo (Robertson 85), O’Reilly (McEleney 46), Patching (Davenport 46), Duffy, Hoban (Mullen 37), McMullan.
Sligo Rovers: McGinty, Wilson, Morahan, Denham, Hutchinson, Henry-Francis, Malley, Chapman (Elding 73), Power, Pearce, Fitzgerald.
Referee: Paul Norton (Dublin)