He steps in for the injured Chris Whitaker to partner Jonathan Sexton at half-back. Fergus McFadden, who impressed on his debut for the province last weekend, retains his place at outside centre, meaning five of Leinster's starting backs for tomorrow are aged 22 or younger.
Right winger Gary Brown will be making his 50th appearance for Leinster against the Scarlets.
In the pack, Argentina's Juan Francisco Gomez starts at prop with Keith Gleeson coming into an all Irish international-back row to partner Shane Jennings and Jamie Heaslip. A decision on stand-in skipper Leo Cullen's fitness will be made closer to kick-off, with 6ft 10in youngster Devin Toner waiting to deputise for him.
Leinster have the opportunity to equal Cardiff's record of 17 successive home wins in the league tomorrow. In Leinster's favour, all eight of the their previous meetings with the Scarlets have gone the way of the home side on the day.
LEINSTER: Rob Kearney; Gary Brown, Fergus McFadden, Christian Warner, Luke Fitzgerald; Jonathan Sexton, Cillian Willis; Juan Francisco Gomez, Bernard Jackman, Stephen Knoop, Trevor Hogan, Leo Cullen (capt)/Devin Toner, Shane Jennings, Keith Gleeson, Jamie Heaslip.
Replacements: Brian Blaney, Stan Wright, Devin Toner/Cian Healy, Cameron Jowitt, Stephen Keogh, Chris Keane, Ross McCarron.