"I had been hitting it kind of bad, not real good, and just to put the new driver in the bag and to get the results that I did today and especially with the putter, I'm very happy."
Gainey switched to a new Callaway driver - Optiforce - and missed only one fairway.
With three days to go, Simpson and Park are hanging close to the top. Park is on his second try at the PGA Tour, returning to the Web.com Tour in 2009 after 16 cuts and only one top-25 finish in 2008.
This year hasn't gone much better for the former Arizona State University player. His best finish is a tie for 31st at the Shell Houston Open, but he has 11 missed cuts in 14 attempts this year.
"I put in a new putter, it's a counter-balance putter," Park said. "The ball seemed to find the hole and I made a lot of long putts today, which hasn't been the case this year. It was a lot of fun watching all those putts go in."
Park ranks 166th on Tour in strokes gained putting.
"I feel like I haven't been putting poorly, I just haven't made a lot of putts," he said. "I was driving it well today, keeping it in play and that helped. I don't feel like I did anything special tee to green, but it was a pretty special day for me on the greens."
Phil Mickelson, who has missed the cut at Old White in his first two tries, struggled on No. 17, which led to a 4-over 74. The projected cut is even-par 140, which means Mickelson will have to shoot at least 4-under today to play through the weekend.
"I played the last two holes 4-over, which is not good," he said. "I was trying to make the birdie at No. 2, thinking if I made a birdie I would be OK heading into (today's) round, but I don't know what it is. I feel like I was playing really well heading into here and I don't play this course well."
Today's second round begins with Chris DiMarco, Jimmy Walker and Daniel Summerhays teeing off on No. 1 at 7 a.m., while Rod Pampling, Richard Lee and Robert Streb at the same time on No. 10.
Contact Assistant Sports Editor Rich Stevens at richstev...@dailymail.com or 304-348-4837.