Dundalk's title hopes suffered a further setback as they were held scoreless by a well organised Derry City side at Oriel Park.
Cork City's 2-1 win over Sligo Rovers on Monday left the reigning champions 16 points adrift at the start of play.
With that in mind, a win was essential for Stephen Kenny's side but they failed to get it, as Derry City left with a well earned share of the spoils.
The champions opened brightly and Ger Doherty was called into action after just three minutes, turning Paddy Barrett's glancing header from Patrick McEleney's floated free-kick around the post.
The Derry City goalkeeper then got a strong hand on a powerful Dane Massey effort six minutes later with McEleney seeing the follow-up deflected wide.
With Rory Patterson absent with a broken foot, the Candsystripes lacked punch up front and failed to create a single opening in the opening 45 minutes.
Dundalk looked the only team likely to fashion an opening and Chris Shields fired a half-volley over the top as the game drifted past the half hour mark.
Things improved considerably after the break with lone Derry City striker Nathan Boyle driving a low effort across the face of the Dundalk goal early in the half.
Jamie McGrath then blazed over from a McEleney cut back before the Derryman located Massey on the left with a delicious pass but the full-back's knockdown just couldn't reach David McMillan.
McEleney required some strapping to his right knee on the hour mark and he was withdrawn six minutes later, Ciaran Kilduff his replacement.
Derry carried much more of a threat at that stage and they almost went in front 60 seconds before McEleney's departure.
Nicky Low's corner from the right came off Sean Hoare and looped towards goal but -luckily for the Dundalk centre-back - Benson was on the post to clear.
The Oriel Park faithful feared the worst when Boyle capitalised on a slip by Hoare in the 76th minute but he hit the side-netting with just Gary Rogers to beat.
Doherty tipped a Michael Duffy drive around the post in the 89th minute but Derry City saw it out relatively comfortably and they almost snatched a win themselves in stoppage time but Aaron McEneff hit the side netting.
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Dundalk: Gary Rogers; Niclas Vemmelund, Sean Hoare, Paddy Barrett, Dane Massey; Chris Shields (Stephen O’Donnell 74), Robbie Benson; Michael Duffy, Patrick McEleney (Ciaran Kilduff 66), Jamie McGrath; David McMillan (Thomas Stewart 79).
Derry City: Ger Doherty; Conor McDermott, Aaron Barry, Dean Jarvis; Harry Monaghan, Lucas Schubert (Josh Daniels 75), Nicky Low, Barry McNamee, Ronan Curtis; Aaron McEneff, Nathan Boyle (Mark Timlin 79).
