April 4 (Reuters) - Kim Si-woo reeled off five birdies in a six-hole stretch en route to the first-round lead at the Texas Open in San Antonio on Thursday.
The South Korean carded six-under-par 66 for a one-stroke advantage over Mexican Abraham Ancer, Venezuelan Jhonattan Vegas and Americans Chris Stroud and J.T. Poston at TPC San Antonio.
Kim's place at next week's Masters is already assured but the four players behind him all need to win on Sunday to punch the final ticket to the first major championship of the year.
Rickie Fowler and Jordan Spieth, among only a handful of the big names using the Texas Open to tune-up for the Masters, both shot 68 on an unusually benign day in a typically windy location.
Spieth more than most could do with a boost in confidence before heading to Augusta National, where his 2015 victory kicked off a major year that with a little luck could have ended with a calendar grand slam.
But he has been out-of-sorts this year so was in an upbeat mood after his round.
"Other than one three-putt it was kind of a bogey-free type round, putting myself in position on those approach shots to make par at worse," he told Golf Channel.
"Swing is getting there, putting stroke feels really good, it's progressing day to day.
"(I'm pleased with) the overall way I attacked the golf course to limit the amount of mistakes."
Fowler, second behind Patrick Reed at the Masters last year, was also pleased with his round.
"It's always nice to get out and make some birdies early, shake off some rust," said Fowler, who skipped last week's WGC-Match Play.
A strong week would also be a nice tonic for world number 61 Kim, who has struggled over the last month.
Starting his round at the 10th, he was plodding along at even par after seven holes, but birdied the next two with putts of five feet before slipping with a bogey at the first.
He responded magnificently with five birdies in the next six holes to grab the lead.
"If I'm reading (the greens) good I can putt well," he said.
(Reporting by Andrew Both in Cary, North Carolina, editing by Nick Mulvenney)