Ireland's Padraig Harrington remains in contention at the Travelers Championship in Connecticut.
The Dubliner posted a second round 69 to remain three shots behind overnight leader Jordan Spieth.
It was a solid round from the three-time major winner who navigated the windy conditions expertly.
McIlroy endured a tougher evening as he struggled to follow up his first round of 67 with a 73 - to make the cut by one shot.
He was in position on the fairway on the 18th for a par - only for his right foot to slip on the greasy surface and he duffed his second shot.
One of these drives is not like the others.
43 (!!) yards longer than the next furthest. pic.twitter.com/Amwmeay6o2
— PGA TOUR (@PGATOUR) June 24, 2017
He eventually posted a bogie to leave him with a nervy wait until the cut-line was confirmed at even-par.
Jordan Spieth leads the way on eight-under - one ahead of Troy Merritt and Patrick Reed.
Jordan Spieth holds the lead.
Patrick Reed makes a charge.#TheTakeaway pic.twitter.com/HJ20zC5xg4— PGA TOUR (@PGATOUR) June 24, 2017
Jason Day missed his second consecutive cut after he carded a second round 70 to leave him on two-over for the tournament.
