"When I eagled, I was like, 'Oh, now I'm 7 (under) through 11, so that's keeping ahead of that 50 percent mark.' But this is a different golf course," he said. "The golf course is much harder than most of the other times I've kind of taken that attitude."
Couples shot his 63 in 1992 in the third round. Norman opened with a 63 in 1994 when he went on to shatter the tournament record at 24-under 264. Along with joining them in the record book, Castro matched the record set by Billy Ray Brown in 1992 with his three-shot lead after one round.
Castro is not well known even in golf circles. His mother grew up in Peru and moved to America as a teenager along with her sister, Jenny Lidback, who played the LPGA Tour. He toiled in the minor leagues for five years after getting his industrial engineering degree at Georgia Tech.
Woods wasn't pleased with how he struck the ball, only with where he missed it. Despite missing six greens, he was left with straightforward shots to save par. The only blemish came at the end, when his 56-degree wedge came up heavy into the grain and failed to reach the putting surface.