Eoin O'Malley joins Paul O'Donohoe, a debutant in the 31-17 Magners League victory over the Scarlets last time out, in the extended squad.
The competition's top point scorer Felipe Contepomi (130 points in 10 games) is also included alongside Rocky Elsom, while the returning Chris Whitaker and Sean O'Brien both take their places in the enlarged panel.
Head coach Michael Cheika will confirm the starting team and replacements on Thursday afternoon.
Speaking ahead of the province's trip to Swansea, forwards coach Jono Gibbes said that the squad are determined to continue their winning ways against a formidable Ospreys side.
"There were a number of positives from the win over Llanelli," he admitted.
"We have been pretty mean this year in terms of conceding tries and even though we let in two against the Scarlets, I felt that we defended superbly at important periods in the game when the pressure was on.
"I was pleased with some of the younger players who took their opportunities. I was especially pleased for Fergus (McFadden) who has had to bide his time.
"He acquitted himself very well and his performance was pleasing for the coaching staff.
"Paul O'Donohoe stepped in, did a good job and he's the latest in a series of good young players coming through our Academy who have performed consistently well this year alongside the likes of Devin Toner, Cian Healy, Jonathan Sexton and Sean O'Brien.
"It's important that players continue to put their hands up for consideration."
Looking at this Friday's opponents, Gibbes added: "The Ospreys are a dangerous team to face at any time of year, but even more so when people think that they will be weak owing to the number of players who are on international duty with Wales.
"We know that that is not the case. They could be in a position to bring back players so we are preparing accordingly.
"They are still an experienced team with the likes of (Filo) Tiatia, Filipo Levi and Marty Holah. I've played alongside Marty for most of my career and he is an outstanding player.
"He's a wonderful exponent of contact ball and will bring a real physicality and maturity, as will Filo. They are two massively important leaders for the Ospreys.
"Everyone knows how competitive the Magners League is. The top three teams are starting to establish themselves and any time you come up against them you know that you're going to be in a battle.
"Certainly it's a challenge that we won't be shying away from. The Ospreys are serious performers in their own backyard and boast a proud record at home. So it's a game that we need to approach in a positive frame of mind."
LEINSTER Squad (v the Ospreys): Backs (11): Paul O'Donohoe, Chris Whitaker, Felipe Contepomi, Jonathan Sexton, Simon Keogh, Isa Nacewa, Gordon D'Arcy, Fergus McFadden, Eoin O'Malley, Shane Horgan, Girvan Dempsey.
Forwards (15): Cian Healy, Brian Blaney, John Fogarty, Bernard Jackman, Stephen Knoop, Stan Wright, Trevor Hogan, Devin Toner, Malcolm O'Kelly, Rocky Elsom, Cameron Jowitt, Shane Jennings, Sean O'Brien, Stephen Keogh, Kevin McLaughlin.