Spaniard Jon Rahm made a stunning start to his professional career with a flawless seven-under-par 64 that gave him a one-shot lead after the first round of the Tiger Woods-hosted Quicken Loan National Thursday. Rahm, who last week was the only amateur to make the cut at the US Open, fired seven birdies at the event which benefits Woods' charitable foundation to lead Venezuela's Jhonattan Vegas by a stroke. "I was really comfortable off the tee with the driver, hitting it good and hitting it straight, so that allowed me to be a little more aggressive and it paid off," Rahm said. The start of the first round at Congressional Country Club in Bethesda, Maryland, was delayed by two hours due to thunderstorms in the area, but it did little to unsettle Rahm. The 21-year-old, who started his round at the 10th, posted three birdies over his first nine holes before picking up another four on the way home. Smooth-swinging South African Ernie Els, Colombian Camilo Villegas and American Bill Haas were in a group of eight a further shot off the pace. Defending champion Troy Merritt carded an even-par 71 after mixing three birdies with three bogeys. Tournament host Woods, who has not competed on the PGA Tour in 10 months, is not playing in his own event as he is still recovering from two back surgeries he had last year. Park out, Ryu in Top-seeded South Korea will be without world No. 3 Park In-bee at next month's LPGA International Crown but 11th-ranked Ryu So-yeon will replace her in the eight-nation team golf event. Park has been nagged for weeks by a left thumb injury and she has already pulled out of next month's US Women's Open, so her absence was expected from the July 21-24 event at the Merit Club in suburban Chicago. But Park's anticipated replacement, ninth-ranked Jang Ha-Na, was unable to play so Ryu was selected to join fifth-ranked Kim Sei-Young, world No. 6 Chun In-gee and eighth-ranked Amy Yang on the South Korean squad. "After the Women's PGA Championship, I met with doctors and my medical team and they strongly recommended rest for my left thumb injury to heal," Park said. "I cannot commit to International Crown this year and giving an opportunity to one of my Korean colleagues seemed more appropriate." The International Crown will feature eight four-woman teams from South Korea, United States, Japan, Australia, Taiwan, Thailand, England and China. Five teams will advance from pool play to Sunday's title-deciding singles matches. — Agencies