MEXICO CITY – It was one hole that cost Rory McIlroy at last week's Genesis Invitational, with the world No. 1 pointing out he played the other 17 holes in even par on Sunday.

McIlroy also added that he took plenty of positives out of his tie for fifth despite the fact he’d started the final round tied for the lead before a double-bogey 7 at the fifth hole dropped him out of contention.

But if it was his approach shot that airmailed the green at the fifth at Riviera that cost him, it was his putter that paid the price. McIlroy revealed following an opening 65 on Day 1 at the WGC-Mexico Championship that he switched back to his regular putter this week after experimenting with a longer shaft in Los Angeles.

“My right arm can get a little high and my right shoulder can sort of roll over, but with a 35 [inch shaft] it sort of puts my shoulder and my right elbow into better position, sort of more on plane with the shaft,” said McIlroy, who leads Bubba Watson and Justin Thomas by one stroke. “Once I got out there, just that [three-quarter inch] difference in the putter, it moves your eye line and you sort of stop seeing your lines the way you usually do.”

Although his putting was solid in Los Angeles, he finished 27^th in the field in putts per GIR, it was vastly improved at Club de Golf Chapultepec where he was fourth in strokes gained: putting (3.62) in Round 1.