Donald needed to finish eight or better at the Harbour Town Golf Links to stay atop the world rankings. He shot an even-par 71 on Sunday to finish at two over par 286 for 72 holes.
He had taken the top spot for the first time in his career after winning the BMW PGA Championship on the European Tour last year. He went on to hold the No. 1 for 40 weeks, a run that ended when McIlroy won at the Honda Classic last month.
Donald then reclaimed the top spot just two weeks after with a victory at the Transitions Championship. Fast forward four weeks later and he is out of the top spot once again.
He was in danger of missing the cut at the RBC Heritage until he managed to save par on the last three holes on Friday and squeezed in by just one shot. Then on Saturday he only was able to muster an even-par round and fell 14 shots behind the leader.
Donald has been a far cry from what he achieved last year when he became the first player ever to officially win the money lists on both the PGA and European Tours.
His finishes this year read like this: T48, T56, T33, T6, 1, T32 and T37.Those are not the kind of performances of a world's No. 1.
Meanwhile, McIlroy—who will turn 23 on May 4—has 11 top five finishes in his last 13 tournaments. He is not expected to play again until the Wells Fargo Championship in Charlotte, N.C. three weeks from now.
Can Luke Donald make it back to No. 1?
Donald did battle in the tournament and never seemed to quit on the course during the weekend, but it just wasn't the Luke Donald we are used to seeing.
He is far too good of a player to stay on this downward slope for too long. Maybe his disappointing performance at the Masters is still on his mind and he needs some time to regroup and come back to being himself on the course.
We'll just have to wait and see.