The Argentinean scored Leinster’s only try after an hour, also gaoling the conversion and three penalties.
However Leinster had to withstand a late Connacht comeback before they could be sure of the points. Tongan centre Andrew Mailei bagged a 76th-minute try for the visitors and only a botched lineout kept the westerners from sneaking the win in injury time.
Australian born fly-half Paul Warwick had given the Westerners an early lead with two penalties, but Contepomi’s first points of the evening reduced the gap to three at the interval, and he added his second to draw the side’s level12 minutes into the second half.
Despite a sin-binning for prop Reggie Corrigan, who launched a fist at Farley at a ruck on the hour, Leinster were able to extend their lead with Contepomi’s try. Guy Easterby fed his skipper metres from the Connacht line, and despite slipping on the sand-laden surface he was able to step inside the tackle of Darren Yapp and go over under pressure from John Fogarty.
The conversion and a further penalty pushed Contepomi past the 2200 point mark for the season but it was then Connacht who pressed and when Mailei crossed for his first league try after a brilliant break from Matt Mostyn they senced a shock victory.
Warwick set up a climactic finish with the conversion, but when Connacht opted to kick a penalty to touch rather than ask Warwick to kick them to a draw, hooker Fogarty´s throw was ruled crooked.