Donegal suffered a second straight defeat in Division One of the Football League as they were surprised by Roscommon as Monaghan lost in Cork.
Roscommon led 0-11 to 0-4 at one stage in Letterkenny and while Donegal reduced the margin to 0-15 to 0-13, a superb Cathal Cregg sealed an away win.
Colm O'Neill hit 1-8 for Cork as they beat the Farney County 1-20 to 1-13.
Cork led 1-5 to 0-0 and while a Conor McCarthy goal cut the margin to four, the Rebels quickly regained control.
The Pairc Ui Rinn result handed Monaghan a third successive Division One defeat and the Farney men now find themselves in a relegation fight alongside the Rebels and Mayo to see who joins doomed Down in making the drop.
O'Neill's seventh-minute goal was the highlight of Cork's fast start as he fired past Rory Beggan after good work by Paul Kerrigan and Peter Kelleher.
Conor McManus opened Monaghan's account in the 11th minute only for Cork to extend their lead to 10 helped by further scores from O'Neill and Kerrigan.
Monaghan looked to be getting back into the game as they scored an unanswered 1-3 with McManus' quick free setting up McCarthy to net.
But Cork responded with the two final scores of the first half to lead by six at the break and two further Rebels points after the restart ended the game as a contest, with the pace dropping in the final quarter.
Monaghan remain the only team to have beaten Roscommon in this year's League after the Rossies produced a tremendous display to see off Donegal.
Donegal's listless first half
Donegal produced a listless opening quarter as Roscommon moved into a 0-7 to 0-1 lead with Ciaran Murtagh, Fintan Cregg and Conor Daly all among the scorers.
The home side could have been even further behind at that stage as Donegal keeper Peter Doyle made a superb save to tip a Daly shot over the bar.
After Niall Daly missed a further Roscommon goal chance, Odhran MacNiallais kicked Donegal's only point from play in the first period, before Karl Lacey was introduced for his first action of the season in place of Eamonn McGee.
Frees from Michael Murphy and Paddy McBrearty cut Roscommon's lead to 0-11 to 0-6 by the break and a superb third quarter by the skipper helped Donegal reduced the margin to two points by the 55th minute.
However, Donegal then suffered a blow as Odhran MacNiallais' afternoon ended following a second yellow card and Cregg's brilliant finish after a sweeping Roscommon move killed off any prospect of the home side completing an unlikely comeback.
Donegal's latest defeat leaves them with their Division One status not yet secured although one victory from their concluding two away games against Dublin and Monaghan will probably secure them a semi-final berth.
Roscommon, now on eight points, are almost certainly already guaranteed a semi-final place.
WEEKEND ALLIANZ FOOTBALL LEAGUE RESULTS
Cork 1-20 1-13 Monaghan
Mayo 0-14 2-13 Kerry
Donegal 0-17 1-19 Roscommon
Meath 1-11 1-17 Tyrone
Laois 1-22 5-10 Derry
Armagh 1-15 1-15 Galway
Longford 0-17 1-11 Tipperary
Kildare 2-14 2-15 Sligo
Offaly 0-15 1-11 Clare
London 1-11 1-16 Leitrim
Carlow 1-07 2-17 Louth
Antrim 1-16 0-06 Waterford
Wexford 4-23 3-14 Wicklow
Down 1-08 1-15 Dublin
Fermanagh 0-09 0-12 Cavan
Limerick 0-07 3-14 Westmeath