Matthew Morgan, the 21-year-old fly-half, ran the show in the first half with his sharp footwork causing Ulster all manner of problems and setting up a try for Sam Lewis that had Ospreys 7-3 up at the break.

Yet Ulster rediscovered their poise after the break and Cave carved open the Welsh defence to swing the game in the home side's favour and establish a lead they never surrendered.

Ulster were forced to soak up substantial Ospreys pressure in the opening minutes with Morgan's burst from fly-half almost seeing him sneak over in the corner.

Morgan was again at the heart of it when Ospreys did take the lead after ten minutes as his jinking run, following Ashley Beck's penetrative burst, resulted in Lewis cantering over. Sam Davies judged the conversion perfectly in the wind.

Ulster delivered the response expected of them by a packed crowd with the forwards first seeing a drive held up over the line before Mike Allen dropped the ball after crossing the whitewash under pressure from Beck.

Yet Ospreys failed to buckle and Ulster's sole reward after 23 minutes was a Ruan Pienaar penalty that reduced the arrears to 7-3.

The home side continued to put pressure on the Ospreys line but the visitors almost extended their lead after another electric Morgan break earned a penalty but Davies was unable to convert.

Diminutive Morgan is a slippery customer at the best of times but with the rain hammering down the fly-half was causing Ulster no end of troubles with his quick footwork and eye for a gap.

Ulster could have narrowed the deficit on the stroke of half-time but Pienaar's penalty was wide of the posts, leaving the Ospreys 7-3 up at the break.

It needed a moment of magic to get Ulster on the front foot and it fell to Cave, starting at inside centre, to supply it as he spotted a gap and burst through to four minutes into the second half.

Pienaar slotted the extras and suddenly Ulster were three points to the good at 10-7.

Ulster thought they had given themselves breathing room in when Pienaar charged down a kick and Iain Henderson powered over only for the TMO to judge the ball had been ripped from him before he could ground it.

The Ospreys were having to dig deep to shut out the their hosts but after weathering the storm they spent the last ten minutes probing for a score of their own.

Ulster managed to clear a scrum from their own five-metre line before a knock-on inside the home side's 22 denied Ospreys another scoring chance, with Eli Walker appearing to injure himself in the move.

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