Horgan is joined in a strong-looking outside backline alongside Gary Brown and Luke Fitzgerald.
Leinster are further boosted by the return of scrum-half Chris Whitaker who partners Felipe Contepomi at half-back, with Michael Berne lining up alongside Christian Warner at centre.
In the pack, Cian Healy is named in a powerful front row alongside Ollie le Roux and Stan Wright, while Leo Cullen captains the side alongside another returning player and fellow Ireland international, Tipperary man Trevor Hogan, who makes his first start after four months on the sidelines.
Cameron Jowitt comes into a strong back-row alongside Keith Gleeson and Stephen Keogh. Shane Jennings misses the game after picking up a knock during the week.
There are promotions for two promising backs from the Leinster Academy. Eoin O'Malley is one of three Old Belvedere backs named on the bench.
After starring for Ireland Under-20s in recent weeks, 19-year-old O'Malley is named alongside last year's Under-20 Grand Slam winner Felix Jones (who shares dual-status with Junior side Seapoint Rugby Club) and Ireland 'A' scrum-half Chris Keane. The trio are joined by Brian Blaney, Stephen Knoop, Devin Toner and Kevin McLaughlin.
Match tickets will be on sale from Ticketmaster outlets around the ground on the day.
LEINSTER: 15: Luke Fitzgerald, 14: Shane Horgan, 13: Christian Warner, 12: Michael Berne, 11: Gary Brown, 10: Felipe Contepomi, 9: Chris Whitaker, 1: Cian Healy, 2: Ollie le Roux, 3: Stan Wright, 4: Trevor Hogan, 5: Leo Cullen CAPTAIN, 6: Cameron Jowitt, 7: Keith Gleeson, 8: Stephen Keogh
REPLACEMENTS: 16: Brian Blaney, 17: Stephen Knoop, 18: Devin Toner, 19: Kevin McLaughlin, 20: Chris Keane, 21: Eoin O'Malley, 22: Felix Jones