Rory McIlroy is leaving no stone unturned before he attempts to become the sixth golfer to complete the career Grand Slam by winning a green jacket at next week’s Masters at Augusta National Golf Club.

McIlroy said he visited swing coach Butch Harmon, Tiger Woods’ longtime coach, in Las Vegas on March 28 for advice after a so-so performance in the PGA Tour’s Florida swing. McIlroy, the No. 2-ranked golfer in the world, tied for 21st at the Cognizant Classic and Arnold Palmer Invitational and for 19th at the Players Championship.

“If there’s one guy that I want to go and get a second opinion from, it’s him,” McIlroy said Wednesday. “Yeah, I think just after the Players and just sort of struggling through that Florida swing with my swing and with some of the misses I was having with my irons, I just thought to myself, ‘I’m obviously missing something here,’ and I just would love to go and get a second opinion and have him take a look, a second set of eyes.”

Harmon, 80, helped Woods win his first eight major championships and also worked with Phil Mickelson and Dustin Johnson.

McIlroy said he met Harmon when he was 14 years old and has consulted with the legendary swing coach at various points throughout his career. He spent about four hours with him in Las Vegas. McIlroy is still working with his longtime coach, Michael Bannon.

“The one thing with Butch is you go spend time with him and you’re always going to feel better about yourself at the end of it, whether you’re hitting it better or not,” McIlroy said. “He’s sort of half golf coach, half psychologist in a way.

“He said a couple of things to me that resonated. It’s the same stuff that I’ve been trying to do with my coach Michael, but he sort of just said it in a different way that maybe hit home with me a little bit more. Yeah, it was a really worthwhile trip and I feel like I’ve done some good work after that. As I said, this is a good week to see where that work has gotten me.”

McIlroy, who is playing in this week’s Valero Texas Open in San Antonio, will attempt for the 10th time to join Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus and Woods as the only golfers to win the Masters, PGA Championship, U.S. Open and Open Championship in the modern era.

In January, McIlroy tied for second at the Dubai Invitational and won the Hero Dubai Desert Classic for a record fourth time the next week. He has struggled to find his form on the PGA Tour, however, with no top-10s in five starts.

McIlroy ranks second in strokes gained: off the tee (.938) but 119th in approach (-.176) and 94th in putting (.036).