Europe lead 10-6 going into the final day with McIlroy first out at 11.05am.
USA captain Justin Thomas has won three out of for points so far and represents the toughest possible opponent.
Europe need 4.5 points today to regain the Ryder Cup and McIlroy, speaking an hour before he was due to tee off, admits he’s under the pump.
“I’m feeling it a little bit right now,” he told Sky Sports.
“It’s a big responsibility leading out the team and trying to get a point on the board early.
“But once you settle into your round, I’ve done this thousands of times before.
“I just need to go out there and play a good round of golf.
“Once I’m out there and hit those first couple of shots I’ll get into it.”
RYDER CUP LIVE: UPDATES FROM DAY THREE AT LE GOLF NATIONAL
Jim Furyk has thrown his big guns out early in a bid to get red on the board to give America hope.
Thomas Bjorn, meanwhile, believes McIlroy is the man who can get Europe off to a flyer.
But the Northern Irishman admitted: “I did not ask to go first. I will play wherever the captain thinks I should play.
“Obviously being a quick player, being at the top of the order becomes a little bit more comfortable for me.
“I went out first at Hazeltine against Patrick Reed. It was a great match and I learnt a lot from that as well.
“I expended too much energy too early in the match and I couldn’t quite keep it up.
“Today is different. We have the crowd behind us this time so hopefully I don’t need to be as animated as that.”
RYDER CUP SINGLES
Rory McIlroy v Justin Thomas
Paul Casey v Brooks Koepka
Justin Rose v Webb Simpson
Jon Rahm v Tiger Woods
Tommy Fleetwood v Tony Finau
Ian Poulter v Dustin Johnson
Thorbjorn Olesen v Jordan Spieth
Sergio Garcia v Rickie Fowler
Francesco Molinari v Phil Mickelson
Tyrrell Hatton v Patrick Reed
Henrik Stenson v Bubba Watson
Alex Noren v Bryson DeChambeau