Fitzgerald was watching from the side as the Welsh region ran out 17-12 victors and Leinster will be seeking revenge in what will be their 50th competitive game at the RDS.
It will be Fitzgerald's first game back since injuring his knee in Ireland's defeat to New Zealand in November and he will be one of four Lions in the home back division, joining Shane Horgan, Brian O'Driscoll and Gordon D'Arcy.
Having helped Ireland win the Grand Slam in 2009, and become a Test Lion in South Africa, Fitzgerald's career took a severe dent when he damaged knee ligaments in the 20-20 draw with Australia at Croke Park in November, 2009.
He missed the rest of the 2009/10 season and only returned at the start of the current campaign. Then he was injured again against the All Blacks, although this time the lay-off was much shorter.
But Fitzgerald couldn't have asked for a better game in which to make his comeback, although he won't be pitting his skills against 2009 Lions team mates Lee Byrne, Shane Williams, Tommy Bowe, Mike Phillips, Adam Jones or Alun Wyn Jones, all of who have been left out of the starting XV for what will be the Ospreys' third game in 11 days.
"If we take our eye off the Ospreys, they will do a job on us. The last time they came over here, they won the league. It's a game we're looking forward to," said Leinster's Irish international flanker Shane Jennings.
"The Ospreys also beat us over there a few weeks ago. So we're up for a big, big game. They have a very good team, a very good squad and whatever lads come over we know we are in for a tough game."