Connor Sammon's early penalty inflicted a third defeat in four games on faltering St Patrick's Athletic to put UCD - now unbeaten in seven games - into the third round of the eircom League of Ireland League Cup.
With six changes in their starting line, compared to St Patrick's five, it was UCD, with the wind at their backs, who started much the better and they could have been three goals up inside 13 minutes.
Bogdan Oprea fired narrowly wide from Sammon's lay off on four minutes before the Students' bright start did bring a goal four minutes later.
Colm Foley pulled down Sammon inside the area as they Saints' defence was caught square to concede a fourth penalty in as many matches.
The Students' big striker sent Brendan Clarke the wrong way from the spot.
Romanian Oprea should have doubled UCD's lead on 13 minutes, but fired wide with the goal at his mercy after sloppy defending gifted him the chance.
Saints quickly came out of their shell and half chances fell the way of Keith Fahey, Mark Quigley and Sean O’Connor before Joseph Ndo shaved the UCD crossbar on 36 minutes with a speculative 25-yard chip.
Saints upped the tempo on the resumption and Ndo's sublime ball over the top put Fahey in on goal within three minutes. Having flicked the ball over Quigley, the Saints midfielder shot into the side netting form a tight angle, however.
The impressive Mark Quigley shot just wide minutes later as Saints maintained the pressure.
But for all their possession, St Patrick's continued to struggle in front of goal and it was UCD who might have doubled their winning margin four minutes from time when Sammon forced a terrific save from Clarke.
St Patrick's Athletic: Clarke; Foley, S Quigley, Paisley; Rooney (Guy, 61 mins), Fahey, Ndo, O'Connor, Frost; O'Neill (Murphy, 79), M Quigley.
UCD: Quigley; Mahon, McMillan, Kenna, Bermingham; Fitzgerald (Kelly, 77 mins), McDonnell, McFaul (McNally, 83), Bolger, Opera (Purcell, 59); Sammon.
