Sean Cronin try helps Leinster edge Ulster in Guinness PRO12
Sean Cronin scored the only try of a bruising and defence-dominated Guinness PRO12 derby as Leinster overcame Ulster 8-3 at the RDS.
Leo Cullen's men claimed a deserved victory to get back on track after two disappointing weeks in Europe, with man of the match Luke Fitzgerald, Josh van der Flier and Martin Moore standing out.
In a cagey first half with few moments of real quality, Ulster's stubborn defence eventually gave way as Cronin drove over from a 36th-minute lineout maul to give Leinster an 8-3 lead. Jonathan Sexton and Paddy Jackson had kicked early penalties.
The Ulstermen, with just one interpro win in Dublin since 1999, stayed in the hunt through some strength-sapping phases. Leinster managed to hold them at arm's length despite some incisive running from Stuart McCloskey and Craig Gilroy.
Ireland out-halves Sexton and Jackson swapped penalties inside the opening quarter-hour, the latter scoring at the second attempt after a strong spell of carrying from the Ulster forwards and big centre McCloskey.
Sexton then found Fitzgerald with a pinpoint cross-field kick past halfway, but the supporting Isa Nacewa - a late inclusion at full-back for Rob Kearney (tight hamstring) - was swiftly bundled into touch.
Leinster carried more of an attacking threat in the second quarter, Sexton's looping pass inviting Fitzgerald forward on the left wing again and Andrew Trimble conceded a five-metre lineout. The hosts were held up from close range and the prolonged spell of pressure near the Ulster posts petered out with a loose Nacewa pass.
The hosts' persistence eventually paid off approaching the interval. Although Robbie Diack denied them initially with an athletic steal, Cullen's side got a second lineout right and the subsequent maul saw hooker Cronin crash over. Sexton missed the left-sided conversion with a poor strike.
A barnstorming run from Rhys Ruddock saw Leinster begin the second period with a bang, however Sexton's inviting pass was knocked on by Ben Te'o with the try-line at his mercy.
Rory Best came to Ulster's rescue as he held up Van der Flier past the whitewash following a powerful run from Tadhg Furlong, and the visitors dug deep to claw back possession and territory, a Peter Nelson kick finally bringing them back into the Leinster half.
It was Leinster's turn to scramble back after Trimble exploited some space on the left wing, but a well-won Moore penalty broke up a promising Ulster spell. Holding the lion's share of possession, Leinster were unable to add to their lead and, frustratingly for visiting boss Les Kiss, the Ulstermen could not get back into scoring range.
Ian Madigan pushed a long-range drop goal effort wide and Leinster relied on their well-organised defence to see them home, tackling to a standstill to claim a very hard-earned victory.