With Dundalk not in action until tomorrow, City knew a win would put them clear at the top, but after going a goal down after only six minutes they needed a penalty and O’Sullivan’s intervention to claim what could be a crucial three points.
Cork boss John Caulfield made two changes to the side that battled to a hard fought 1-0 win in Drogheda last week, with the suspended John Dunleavy and Gavin Kavanagh missing out. Their places went to Dan Murray, back from suspension, and Liam Kearney.
UCD, who went seven league games without a win until last weekend’s impressive 1-0 victory over European giant-killers Sligo Rovers, kept faith with that starting 11.
The home side were guilty of some sloppy passing and giving the ball away far too easily early on and Aaron Callaghan’s young side were quick to make them pay and were in front after only six minutes.
Last week’s scorer Samir Belhout crossed low from the right and Robbie Creevy found himself in acres of space to side-foot home from 15 yards. It was the first goal keeper Mark McNulty had conceded since Rory Gaffney scored for Limerick on May 20.
City should have hit back almost immediately but Murray dragged his effort wide from six yards.
O’Sullivan went close in the 16th minute when his header from a superb Billy Dennehy cross was tipped away by keeper Conor O’Donnell.
O’Donnell then tipped Colin Healy’s rasping drive over the bar and Murray then put his header narrowly over the top from the resulting corner.
Buckley should have done better when he headed over unmarked in the 24th minute before Creevy almost shocked City again, his header forcing McNulty into a flying save.
In a rip-roaring first half, O’Sullivan again went close in the 29th minute when O’Donnell made a great save with his legs.
The game was turned on its head four minutes later when Kearney found O’Sullivan, who showed a quick turn of pace to outstrip Hugh Douglas and the UCD defender hauled the striker down inside the box.
Referee James McKell had no option but to brandish a red card at Douglas for denying a clear goalscoring opportunity, and Billy Dennehy made no mistake from the spot for his 11th goal of the season.
UCD suffered another blow on the stroke of half-time when they lost goalscorer Creevy to injury.
Caulfield introduced new signing John O’Flynn for O’Leary at half-time as he went with two up front for the second half and the pressure almost paid immediately when Matthews had to hack Josh O’Shea’s effort off the line just a minute in.
O’Flynn should have scored in the 71st minute but man of the match O’Donnell made another great save with his legs as City threw everything at the 10 men.
The pressure finally told four minutes later when O’Sullivan headed home Colin Healy’s inswinging corner, much to the relief of the home support.
The inspired O’Donnell made another two magnificent stops to deny O’Flynn and then Kearney late on as City finished the stronger.
CORK CITY: McNulty, Lenihan, Murray, D. Dennehy, B Dennehy; O’Shea (O’Shea 60), O’Leary (O’Flynn 45), Healy, Buckley (Morrison 76), Kearney; O’Sullivan.
UCD: O’Donnell; Matthews, Douglas, Kavanagh, Langtry; Belhout, Crowe, Creevy (Coyne 45), Benson, Molloy (Ben Mohamed 66); Cannon (Simon 73).
Referee: James McKell (Tipperary).