Hideki Matsuyama hoping for return to form

World number four Hideki Matsuyama lost his red-hot form from early this season but hopes a return to Muirfield Village will revitalise him at the Memorial Tournament starting on Thursday.

Japan's Matsuyama, who won his first PGA Tour event at the 2014 event hosted by Jack Nicklaus at the challenging course he designed, has struggled recently after a superb start to the season.

"It has been an up-and-down year," Matsuyama, 25, told reporters on a practice day at the Ohio layout. "Hopefully I'm on the upswing, but to be honest, my swing isn't where I'd like it to be and I'm not putting very well.

"Coming back to Muirfield Village, there are some special vibes here and hopefully that will encourage my game to play much better than I have been the last couple of months."

Matsuyama won the WGC-HSBC in Shanghai at the start of the wrap-around PGA Tour season, captured the Hero Challenge, Tiger Woods' unofficial charity event in the Bahamas, and claimed his fourth career Tour win at February's Phoenix Open.

Since then, his best result was a tie for 11th at the U.S. Masters and his general play slumped as the talented Japanese broke 70 in just eight of 22 rounds since his Phoenix win.

This invitational, contested by an elite field of 120, is a key test with the U.S. Open looming two weeks later at Erin Hills in Wisconsin.

Frustrated by unreliable putting, Matsuyama tried a switch to a center shaft putter but has gone back to his old flat stick.

"I've been practising a lot with the center shaft putter, hoping to find something, to find a good feeling, to find something that suits me. But unfortunately I haven't," he said.

"So I've gone back to my Ace putter this week and hopefully that will wake up and do some good."

Other featured players include world number one Dustin Johnson, number three Jason Day, one of a dozen Australians in the field, sixth-ranked Jordan Spieth and Players Championship winner Kim Si-woo of South Korea.

"Winning here three years ago, I didn't realize how big a tournament this really is," Matsuyama said. "I've come to realize what an important event the Memorial Tournament is.

"There's a different feel here at the Memorial Tournament, whether it's the course, the fans, Mr. Nicklaus hosting, it's a special event and always will be to me."