The recently-formed Italian franchise - without a win in their RaboDirect Pro 12 history - will rue 12 points missed by the boots of their half-back pairing of Tito Tibaldi and Daniel Halangahu, while Ulster proved considerably less wasteful, O'Connor contributing 17 points to top up the 10 supplied by a Paddy Wallace score and a late penalty try. Ulster remain six points clear at the top of the table after this fixture, rescheduled from September as a mark of respect for the late Nevin Spence.

With several key players lost to injury, and half a team's worth involved in the Ireland XV 53 - 0 demolition of Fiji on Saturday, numerous fringe players were given the opportunity to shine in today's starting line-up at the Stadio XXV Aprile. A youthful backline comprised Ricky Andrew at full-back, Michael Allen and Chris Cochrane on the wings and Michael Heaney at scrum-half - holders of only 14 caps between them to date - alongside the more experienced heads of Wallace and Jared Payne in the centre, and O'Connor at out-half. The forwards had a more familiar look, although personnel restrictions meant Robbie Diack and Nick Williams played out of position, at lock and blindside flanker respectively.

After a slow opening to the game from both sides, Ulster broke the deadlock on 10 minutes courtesy of O'Connor's close-range penalty, but the Zebre reaction was immediate, Dries van Schalkwyk rising highest to collect Halangahu's restart, and swiftly supplying Tibaldi, who ran over unopposed before sluggish Ulster had a chance to react. Halangahu's conversion attempt was not quite as accurate as his restart had been, however, and the score sat at Zebre 5 Ulster 3.

Zebre continued to make the running for the next 10 minutes, even stealing possession at the Ulster lineout early in the second quarter to apply some extra pressure, before solid defence from the visitors allowed Heaney to clear his lines. A promising Ulster break then came to an end when Cochrane just ran out of terrain on the left wing, but with Zebre penalised for coming off their feet on 25 minutes, O'Connor nudged his side back in front with the boot.

Once Tibaldi had narrowly missed a penalty attempt from half-way, the Parmesans appeared to run out of steam temporarily, with O'Connor adding to his tally on 33 minutes after sloppy Zebre defending. As half-time approached, however, the hosts' rhythm returned, and only assiduous defending from Roger Wilson on his own try-line prevented the concession of a second score after strong ball-carrying from the Italian forwards had made the try look an inevitability. There was just enough time, however, for Halangahu to knock over a penalty seconds before the break and bring the difference down to a single point.

Half-Time Score Zebre 8 Ulster 9

A crucial missed tackle early in the second period after Tibaldi's clever reverse pass opened a fissure in the Ulster line which Halangahu exposed expertly, pulling off a sharp dummy and racing for the corner in the 43rd minute. The out-half just failed to convert his own score, however, leaving Ulster only four points adrift, three of which O'Connor gratefully clawed back four minutes later with a penalty from outside the '22'.

But Ulster continued to make life difficult for themselves, firstly with the concession of a 52nd-minute penalty, which Halangahu struck against the post, and then through more inert play, as Zebre were first to the rebound and, a lineout later, van Schalkwyk powered past Allen to touch down try number three. Halangahu's conversion was again narrowly off-target, leaving the gap at Zebre 18 Ulster 12 when more accurate goal-kicking from the hosts would have closed the game out by this stage.

Ulster's response was patient and composed, as they moved the ball from left to right after strong mauling metres from the Zebre line, until Allen capitalised on a marginal gap to put Wallace in by the right-hand corner flag. O'Connor was unlucky to see his conversion hit the woodwork, but with Italian centre Mario Pratichetti sinbinned for not rolling away in Ulster's very next attack, the out-half atoned for the miss on 62 minutes with his fifth successful penalty, making it Zebre 18 Ulster 20.

Poor reception again by Ulster straight from the restart put them right back under pressure, and with van Schalkwyk driving over from a five-metre scrum awarded after Heaney had illegally carried the ball over his own try-line, Zebre secured their bonus point on 65 minutes. This time Halangahu's conversion split the posts, and left Ulster requiring a converted try to maintain their 100% record with the score at Zebre 25 Ulster 20.

Their first attempt to salvage the match in the last 10 minutes came to naught thanks to an unfortunate knock-on metres from touch, but the second - from a scrum just outside the Zebre 5-metre line - proved more successful, as referee Neil Patterson awarded the penalty try after adjudging the Italian front row to have stood up in order to unfairly prevent the try. O'Connor did the needful from in front of the posts to edge his side two points to the good.

With Zebre now frantically scampering to find points from any quarter, Ulster held their nerve and their discipline over the remaining minutes, to leave Parma with a fortuitous victory and their unbeaten record intact.

Full-Time Score Zebre 25 Ulster 27

Zebre
(15 - 9) D Odiete; L Sarto, M Pratichetti, S Pace, A Castagnoli; D Halangahu, T Tebaldi
(1 - 8) M Aguero, A Manici, L Redolfini, F Cazzola, J Sole, F Ferrarini, F Cristiano (c), D van Schalkwyk
Replacements (16 - 23) A de Marchi, S Perugini, F Tripodi, E Caffini, N Belardo, A Chillon, N Cattina, R McCann

Ulster
(15 - 9) R Andrew; M Allen, J Payne, P Wallace, C Cochrane; N O'Connor, M Heaney
(1 - 8) C Black, N Brady (c), J Afoa, R Diack, N McComb, N Williams, M McComish, R Wilson
Replacements (16 - 23) R Herring, T Court, D Fitzpatrick, J Simpson, A Birch, B McIlroy, S Olding, P Nelson