Philadelphia (USA), May 9 -- Rory McIlroy admitted he felt "a little rusty" after he began his warm-up for next week's US PGA Championship by finishing five shots behind round one leader Keith Mitchell at the Truist Championship in Philadelphia.

McIlroy - last year's winner and a four-time champion at the event - recorded six birdies and two bogeys to card a four-under-par 66 at the Wissahickon Golf Course on Thursday.

The 36-year-old, who completed a career Grand Slam with his thrilling win over Justin Rose at last month's Masters, ended the day tied in 25th alongside nine other players, the BBC reported.

"I was a little rusty out there, just hadn't played in a week and I hadn't really done a ton of practice," said McIlroy.

"I drove th...