A late rally from Leinster carried them to a narrow Guinness PRO14 victory over 14-man Benetton Treviso at the Stadio Comunale di Monigo.
The Italians led 27-22 with 20 minutes left, helped by 12 points from debutant fly-half Ian Keatley, but Dave Kearney scored his third try and replacement Harry Byrne sent over a penalty to give the reigning champions a bonus point in a 32-27 victory.
Harry Byrne had come on for his older brother Ross in the 68th minute to make his debut.
Both teams, who have played several memorable matches in recent seasons, were severely depleted by World Cup call-ups.
It was the visitors who made the better start, with Ross Byrne slotting over an early penalty before converting a 14th-minute try from Adam Byrne.
Treviso hit back strongly, though, with tries in quick succession from Derrick Appiah and Tomas Baravalle, both converted by Keatley.
But it was Leinster who led 17-14 at half-time thanks to a converted try from Kearney moments before the hooter.
Former Munster stalwart Keatley quickly drew the hosts back level with a penalty, but they were then reduced to 14 men in the 49th minute when Iliesa Ratuva Tavuyara was shown a red card for taking out Kearney when he went for a high ball.
Kearney immediately crossed for his second try, but another penalty from Keatley and a converted try scored by Luca Sperandio boosted hopes of a Treviso win, only for Leinster to turn things around once more.
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