Centre McFadden injured his knee in the European Cup against Toulon and it was feared his season would be over.
But with the RaboDirect PRO12 play-offs around the corner O'Connor, and Leinster, could be in for a timely boost.
A win against Edinburgh on Saturday would seal top spot in the league, and a home league final, if they win their semi-final.
Leinster came through their 22-20 victory against Ulster on Friday night in good health with no players reporting injury problems.
And O'Connor is delighted with his side's condition.
"We came out quite well from the weekend. There are no bangs or bruises that are going to cost blokes a game," O'Connor told the Irish Times.
"You know we are pretty confident where we are, probably with 28/30 players as opposed to 23.
"Fergus is very close to playing this week, he has progressed very well. You know he will put himself in the frame, hopefully this week."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTubechannel for extensive match highlights and sign up for our newsletter for regular updates on the RaboDirect PRO12.
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland