(CNN) -- Rory McIlroy reclaimed golf's No. 1 ranking without lifting a club after Ryder Cup teammate Luke Donald finished down the field in 37th at the RBC Heritage on Sunday.
Donald needed a top-eight finish to hold off the Northern Irishman but a four-over-par 75 in the opening round put him on the back foot straight away and he eventually finished 16 shots behind the winner, Carl Pettersson of Sweden.
McIlroy took the week off following a disappointing showing at the Masters, traveling to Copenhagen to support his tennis-playing girlfriend Caroline Wozniacki at her home tournament. The Dane's bid for a third successive title in the event ended in defeat in Sunday's final.
McIlroy is next scheduled to play at the PGA Tour's Wells Fargo Championship at Quail Hollow, beginning May 3 -- a tournament he won in 2010.
"#1 again without touching a golf club this week.... I wish it was that easy!" the 22-year-old tweeted on Sunday.
Donald and McIlroy have swapped places three times this year already. The Englishman's latest stint at the top lasted four weeks.
"Is it a concern? No," Donald said. "Obviously, I'd have liked to have played a bit more consistently this year. I built it up nicely last year through tournaments and winning a bunch."
Donald made the cut at the RBC Heritage with a second-round 69 but finished the tournament with two level-par rounds to end up on two over.
"Not my best week, getting used to leaving this place ranked #2. Nice week off now," tweeted Donald, who lost out to Brandt Snedeker in a playoff at last year's tournament.
Donald won the Transitions Championship in March but has only one other top-10 finish. McIlroy has four top-five finishes to go with his Honda Classic win in March.
Donald is next due to play at the Zurich Classic, beginning April 28.
Pettersson, meanwhile, began the final round with a one-shot lead over Colt Knost and finished with a confident two-under 69 to move clear of the field for his fifth PGA Tour title.
Knost had a disastrous final round of 74 to drop out of contention, leaving Pettersson to claim victory by five strokes from another American, Zach Johnson.
Three years ago, the 34-year-old Pettersson dropped 30 pounds in a bid to slim down and improve his fitness, but found his swing was compromised and quickly decided to revert to his previous weight.
Describing how he put the pounds back on, Pettersson told the PGA Tour website: "Well, you drink 10 beers and (eat) a tub of ice cream before bed."