England's Paul Casey fired a seven-under par 65 to own a two-stroke clubhouse lead as darkness halted Thursday's opening round of the 84th Masters. Casey, chasing his first major title, matched the lowest major round of his career to seize the lead over Americans Webb Simpson and Xander Schauffele. Also on the course at five-under through 10 holes was American Justin Thomas, who opened with four birdies in his first five holes and birdied the 10th before play was halted. A thunderstorm struck only 35 minutes after competition began at Augusta National and idled the field of 92 for nearly three hours, ending any chance of the late starters finishing before sunset. That was even with the tournament sending threesomes off the first and 10th tees in a bid to make the most of reduced autumn daylight compared to its usual April date, Covid-19 having caused the postponement and forced a ban on spectators. World number one Dustin Johnson and England's Justin Rose were both three-under through nine holes. Four-time major winner Rory McIlroy, trying to complete a career Grand Slam with a Masters victory, was on level par through nine holes. McIlroy would join Woods, Nicklaus, Gary Player, Ben Hogan and Gene Sarazen as the only career Slam winners with a victory. Johnson is trying to win his second major title and become the first top-ranked player to win the Masters since Woods in 2002. js/bb