Rory McIlroy outscored his playing partner Tiger Woods by a single shot to move into contention at The Memorial last night.
The world No.1 shot a solid two-under 70 in tricky conditions at Muirfield Village to sit four off the lead.
In his first tournament since lockdown, Woods started and finished with birdies for a 71. Brooks Koepka, the third superstar in the group, also birdied the final hole for a level-par 72.
Tony Finau held the clubhouse lead after a brilliant opening 66 which included nine birdies.
Jon Rahm, who shot a 69, said: “It is amazing Tony shot six under. I did not see those scores out there today. I thought anything around even par would be unbelievable which still is.”
The Memorial Tournament is the second PGA Tour event in as many weeks to be held at Muirfield Village Golf Club, and those competing in both ends of the unusual double-header were greeted with a whole new course and much stiffer challenge on Thursday.
Faster greens, different hole locations and longer rough were among the notable changes during first-round action on the Jack Nicklaus-designed layout.
Defending Memorial champion Patrick Cantlay shot an opening two-under-par 70, after finished joint seventh last week.
On the new course, Cantlay said: "Obviously, a lot faster. The greens I think are a lot firmer even than they appear.
"You can get some action on it from the fairway, but even shots last week out of the rough would stop, and today that wasn't the case."
The PGA Tour had to scramble to fill a gap in its schedule when the John Deere Classic in Illinois was cancelled due to state-related challenges regarding the Covid-19 pandemic.
The solution was the creation of the Workday Charity Open and staging it at Muirfield Village, which marks the first time since 1957 the PGA Tour has played two weeks in a row on the same course.
Collin Morikawa, who won last week at Muirfield in a playoff, noticed the changes.
"Today when we stepped on the course, even though it was morning you could start seeing a little shine, so you know the first bounces were skipping a little more, getting a little firmer," Morikawa said after a 76.
"The rough has obviously just kept growing. You miss in some spots, sometimes you've got to chip out and you never know what kind of lie you're going to get, but for the most part it's not going to be good."
