HEINEKEN CUP Quarter-final: Saturday, April 2Leinster v Leicester Tigers, Lansdowne Road, 5.15pm (live RTE 2, Sky Sports 1)
Director of rugby Declan Kidney - protecting the only unbeaten record in the tournament this season - has made three changes from the side which ended their Pool 2 campaign on a high - trouncing Treviso 57-17 - in January.
D'Arcy's inside centre berth goes to Felipe Contepomi, with the Ireland midfielder expected to play some part in the eagerly-awaited last eight clash.
Contepomi links up with Ireland captain Brian O'Driscoll - who sat out last Friday's 31-25 Celtic League win over Llanelli with a tight hamstring.
D'Arcy meanwhile, has played just sixty minutes of rugby for Leinster since injurying his hamstring in Ireland's Six Nations win against Italy in February.
Better news comes as Horgan - Europe's top try scorer (7) - resumes his place on the right wing, with Leinster's other switches coming up front.
Talented 22-year-old flanker Ciaran Potts will make his first start in the Heineken Cup, having previously made three appearances as a replacement.
Kidney is set to whittle his eight named replacements down to seven in due course, with Kieran Lewis the extra man.
Both Potts and fit-again international Keith Gleeson have displaced Shane Jennings and Victor Costello in the Leinster's starting line-up, with Eric Miller shifting from blindside to the base of the scrum.
Due to leg injuries, 23-times capped Ireland flanker Gleeson has not featured in a European game since scoring a try in Leinster's 32-21 Pool 3 loss to Biarritz Olympique in January of last year.
Lining up against Kidney's charges will be Ireland star Geordan Murphy - and the Tigers have set up a fascinating duel between the Naas flyer and international team mate Denis Hickie by naming him on the right wing.
Tigers head coach John Wells has made three changes from the side which lost 23-22 to the Leeds Tykes in the Zurich Premiership last Sunday.
Utility back Sam Vesty starts in Murphy's usual role of full-back, with England international Austin Healey losing out in the backline shuffles.
Up front, England prop Graham Rowntree returns at loosehead, while international flanker Lewis Moody replaces Will Johnson - the benched brother of Leicester skipper Martin Johnson.
Former England and Lions captain Johnson will make his 50th Heineken Cup appearance in Dublin.
The 2001-and-2002 champions suffered a late blow this afternoon when lock Ben Kay failed a fitness test on his injured ankle. Also in the wars was England prop Julian White - who sustained a shoulder blow during a "live scrummaging" session earlier this week - but the 31-year-old is fit enough to start.
2004/05 Form: Leinster: W25-9 v Benetton Treviso (away), W30-11v Bath (home), W92-17 v Bourgoin (home), W26-23 v Bourgoin (away), W27-23 v Bath (away), W57-17 v Benetton Treviso (home)Leicester: W37-6 v Calvisano (home), L8-23 v Biarritz Olympique (away), W37-31 v Wasps (away), W35-27 v Wasps (home), L17-21 v Biarritz, W62-10 v Calvisano (away)
Top Scorers: Leinster: David Holwell 96 points; Shane Horgan 7 tries; Leicester: Andy Goode 81; Harry Ellis 5
Previous Meetings: Leinster 3, Leicester 3(1996: Leinster 10 Leicester 27; 1997: Leinster 16 Leicester 9; Leicester 47 Leinster 22; 1999: Leinster 27 Leicester 20; 2000: Leicester 10 Leinster 32; 2002: Leicester 28 Leinster 18)
Best Finishes: Leinster: Semi-finalists, 1995/96, 2002/03Leicester: Winners, 2000/01, 2001/02
(15) Girvan Dempsey
(16) Emmett Byrne(17) David Blaney(18) Des Dillon(19) Victor Costello(20) Shane Jennings(21) Brian O'Meara(22) Gordon D'Arcy(23) Kieran Lewis
Leicester Tigers: Sam Vesty; Geordan Murphy, Ollie Smith, Daryl Gibson, Leon Lloyd; Andy Goode, Harry Ellis; Graham Rowntree, George Chuter, Julian White, Martin Johnson (Capt), Louis Deacon, Lewis Moody, Neil Back, Martin Corry.Replacements: James Buckland, Darren Morris, Will Johnson, Henry Tuilagi, Scott Bernand, Alesana Tuilagi, Austin Healey.
Referee: Joel Jutge (France)