(Reuters) - Ernie Els put behind him a fear over potential kidney stones and the disadvantage of no pre-tournament practice rounds this week as he surged into contention for the Quicken Loans National in Virginia on Thursday.
The big South African, who has struggled for consistency on the 2014-15 PGA Tour, fired a seven-under-par 64 on a rain-softened layout at Robert Trent Jones Golf Club in Gainesville to end the opening round just one stroke off the lead.
Els was delighted to shoot his lowest score on the U.S. circuit this season, having pulled out of Wednesday's pro-am competition after experiencing pain in his right side before medical tests confirmed it was just a muscle spasm.
"I haven't played with a lot of confidence and you can't play this game without having confidence," Els told Golf Channel after rocketing up the leaderboard with an eagle at the par-five 14th, six birdies and a bogey.
"I didn't have the most perfect warm-up into the week. I didn't play any practice round or in the pro-am but I felt good this morning and my putter felt good.
"I kind of like the course so I just fed off a little bit of Presidents Cup experience, and I played quite nicely."
Els, a four-times major champion who is popularly known as the 'Big Easy' represented the Internationals against the U.S. in the 1996 and 2000 Presidents Cups staged at Robert Trent Jones Golf Club.
That familiarity with the course was certainly a bonus for the 45-year-old South African after his concern over possible kidney stones earlier in the week.
"I've got an L-10 (problem) and normally the pain shoots into my left side," said Els, who has not won on the PGA Tour since his victory at the 2012 British Open.
"The pain was kind of on my back and then it went to the right and I thought maybe it was kidney stones. I guess I am just a wuss.
"It was pretty sore, and they say kidney stones are really, really painful. Luckily there was nothing wrong. It's just a muscle spasm."
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Greg Stutchbury)