Inside centre Gordon D'Arcy has been withdrawn from the Leinster side to face the Ospreys at the Liberty Stadium tomorrow night.
The Ireland centre was initially included for Magner's League clash despite limping off injured in last weekends heavy defeat to Toulouse in France.
His place, alongside Ireland and Leinster captain Brian O'Driscoll, will now be taken by Argentinean Felipe Contepomi, with Jonathan Sexton starting at outhalf. Christian Warner takes Sexton's place among the replacements.
Girvan Dempsey, who suffered a similar fate at the Stade Ernest Wallon, was not included in the squad earlier in the week and will be replaced by Rob Kearney. Luke Fiitzgerald will start on the left wing.
Scrumhalf Cillian Willis replaces Chris Whitaker, who is out for 10 weeks after breaking his leg against the French side.
After an appearance from the bench last week Cameron Jowitt starts at blindside flanker beside number eight Kevin McLaughlin and Ireland international Keith Gleeson.
Like Gleeson, prop Stan Wright and lock Leo Cullen keep their places, but Bernard Jackman is replaced by Ireland 'A' hooker Brian Blaney.
Gary Brown and Warner are on the bench alongside the experience of Jackman and Malcolm O'Kelly, as well as Shane Jennings and scrumhalf Chris Keane, who returns from injury. A decision on whether to name Cian Healy or Ollie le Roux as replacement prop will be made closer to kick-off.
Fullback Kearney who made senior debut in the Liberty stadium and won his 50th Leinster appearance in Toulouse at the weekend, says the side are eager to put in a big performance after the 33-6 defeat to the French giants.
"No-one is more determined than the players and the coaching staff to get our performance right on Friday. We set the highest standards for ourselves and, to be honest, the short five-day turnaround is the perfect medicine to get back on the horse and hopefully back to winning ways," said the youngster today.
"Okay, there are bumps and bruises and we have lost a few players through injury, but everybody is looking forward to the game. That's always the same whenever you put on the Leinster shirt. There are places up for grabs and once the warm-up begins the bumps and bruises tend to disappear and you just get on with the task in hand.
"The Ospreys have fantastic strength in depth but they will be missing a few players through international commitments. Irrespective of that, it's no secret how difficult it is to win in Wales.
"Last weekend's defeat in Toulouse came down as much to individual errors as opposed to anything else. Our concentration wasn't as good as it had been the previous week, but we're all really looking forward to the challenge against an excellent Ospreys side."
Ospreys are without 17 players. Nine are on international duty as Wales prepare to face world champions South Africa, while eight others, including Ryan Jones, Shane Williams and Justin Marshall, are injured.
Assistant coach Sean Holley said today: "Leinster will arrive highly motivated following their defeat in France last weekend and they will be looking to avenge two previous narrow defeats at the Liberty Stadium. We have a strong home record, fine support and the players in our team will be looking to make a point in advance of the fixtures against Harlequins and Ulster."
"There will be a number of fine players on show from both sides in what should be another quality Magners League fixture. With there being no autumn internationals in Ireland this season it is clear that Leinster will field a strong side which will give our players added motivation to set the standard for the Ospreys players on duty with Wales to follow on Saturday."
Leinster: Rob Kearney; Shane Horgan, Brian O'Driscoll (c), Gordon D'Arcy, Luke Fitzgerald; Felipe Contepomi, Cillian Willis; Stan Wright, Brian Blaney, Juan Gomez; Leo Cullen, Devin Toner; Cameron Jowitt, Keith Gleeson, Kevin McLaughlin
Replacements: Bernard Jackman, Cian Healy / Ollie le Roux, Malcolm O'Kelly, Shane Jennings, Chris Keane, Jonathan Sexton, Gary Brown
Ospreys: Gareth Owen; Nikki Walker, Mark Taylor, Andrew Bishop, Aled Brew; Shaun Connor, Martin Roberts; Paul James, Richard Hibbard, Adam Jones; Andy Lloyd, Lyndon Bateman; Hale T-Pole, Marty Holah, Filo Tiatia (c)
Replacements: Ed Shervington, Andrew Millward, Mike Powell, Tom Smith, Rhodri Wells, Ashley Beck, Jonathan Vaughton
