Keith Mitchell used a late birdie run to shoot a 9-under-par 61 and take the early lead at the Truist Championship on Thursday in Flourtown, Pa.

Mitchell started his first round at the Philadelphia Cricket Club’s Wissahickon Course on the back nine and parred his first five holes. After birdieing Nos. 15, 17 and 18, he stayed hot on the front nine with a 6-under 29 coming in, including four straight birdies at Nos. 5-8.

At day’s end, it was only good for a one-stroke lead over Denny McCarthy. Tied for third at 7-under 63 are Collin Morikawa, Rickie Fowler, Akshay Bhatia and Austria’s Sepp Straka.

McCarthy had a five-birdie run, Fowler posted a front-nine 29 and Morikawa went bogey-free in his first competitive round with new caddie Joe Greiner as the Wissahickon Course made its PGA Tour debut. The Philadelphia Cricket Club is serving as a temporary host for the $20 million signature event while Quail Hollow prepares to host the PGA Championship next week.

Ireland’s Shane Lowry and U.S. Ryder Cup captain Keegan Bradley were part of a tie for seventh at 6-under 64. A massive tie at 65 included Patrick Cantlay, Harris English, Tony Finau, Russell Henley, Japan’s Hideki Matsuyama and South Korea’s Si Woo Kim.

Rory McIlroy is the four-time champion of the event at Quail Hollow, including last year, and he managed an opening 66 with six birdies and two bogeys. Justin Thomas, Max Homa and Will Zalatoris are among those tied with him at 66.

Only five players failed to shoot even par or better, including Canada’s Adam Hadwin (1-over 71) and Lucas Glover (2-over 72). There will be no cut after 36 holes.