McIlroy finished behind Wallace by 11 shots at the PGA Championship held at Wentworth. His wife and kids were in the crowd to watch.
The Irishman scored three holes under 5, however, it was a major struggle for him on the back nine for him to return home in 42, making that the worst round he has played since his 79 at The Open, where he was not able to make the cut.
Wallace scored a spectacular 65, made up of five birdies and one eagle. It brought him ahead of Rahm and Stenson by shingle shot.
Wallace candidly expressed his joy at winning. He attributes part of his win to a wonderful start that built up his confidence for the remainder of the game.
McIlroy, a favourite following his win at the FedEx Cup, played a birdie in his fifth and an eagle in his fourth. It was a good start, but unfortunately, after that, his game unraveled and from the eighth, he dropped 3 consecutive shots. This was the start of his losing streak. He has his job cut out for him on Friday, the first stage to qualifying for the Ryder Cup 2020 in Wisconsin.