VIRGINIA WATER, England — Even as he took apart Wentworth with one of his best rounds of 2018, Rory McIlroy knew something wasn't quite right.

"There was still enough loose shots in that first 36 holes to know that, OK, it's not quite there," McIlroy said of the three-shot lead he held going into the weekend at the BMW PGA Championship.

So it didn't really come as a surprise to the former world No. 1 that his game slightly unraveled on Saturday and Sunday.

McIlroy followed up his masterful 7-under 65 on Friday — "the best round I've ever seen," according to playing partner Alex Noren — with scruffy rounds of 71 and 70 to come up short at the European Tour's flagship event.

He finished in second place on Sunday, two shots behind Francesco Molinari.

McIlroy has been working on some swing changes with coach Michael Bannon in Florida, and he said it was a work in progress.

"When you're working through a bit of a swing change or a swing tweak, it takes more than a week's work to try to bed it in," McIlroy said, "and this is my first competitive start since trying to rectify things.

"I think as a tournament goes on," he added, "you're not spending as much time on the range because you're into play mode. Maybe just got away from few of the things I was working on at the start of the week, which is the way, when you get under pressure and you're forced to hit shots out on the golf course, you revert back to what you've been doing. There was a bit of that."

The Arnold Palmer Invitational remains McIlroy's only win in 2018. He has three other top-five finishes but has also missed three cuts and failed to complete the career grand slam after a disappointing final round in the Masters.

"It's close, it's very close," he said. "I've given myself a great chance here this week. I didn't quite pull it off but it's not far away. I get a bit down on myself because my expectations are high, and with a 36-hole lead, I should have closed it out this week."