A hole-in-one helped Si Woo Kim to open up a four-shot lead after the second round of the Valero Texas Open, with Jordan Spieth and Rickie Fowler among the chasing pack.

Kim held the overnight lead in the PGA Tour event in San Antonio, but slipped into an eight-way tie for first place, before a back-nine surge saw him reach 12 under for the tournament.

The South Korean holed birdies at five, eight, 12 and 14, but his ace at the 16th was the highlight.

The 23-year-old is seeking to add to the Tour victories he recorded in the 2016 Wyndham Championship and the 2017 Players Championship.

What a line.
What a shot.
What a statement.
What a celebration.

Si Woo Kim makes an ACE at the par-3 16th.#LiveUnderPar pic.twitter.com/7YYC7n7PiX
— PGA TOUR (@PGATOUR) April 5, 2019

Attempting to reel in Kim over the weekend are the members of a six-way tie for second.

Spieth and Fowler both carded four-under rounds of 68 on Friday, to join their fellow Americans Harold Varner III and Adam Schenk, Canadian Corey Conners and Kim's countryman Lee Kyoung-Hoon at eight under.

World number eight Fowler had held a share of the lead, but successive bogies at 15 and 16 undermined his charge, while Spieth also dropped shots at the first, 10th and 12th. The three-time major winner responded confidently, though, making an eagle and five birdies, including successive birdies to finish at 17 and 18.

Once tied for the lead, @RickieFowler made back-to-back bogeys and trails Si Woo Kim by three. pic.twitter.com/qXMaTojJc1
— PGA TOUR (@PGATOUR) April 5, 2019

Talking his way up the leaderboard. @JordanSpieth keeps it interesting on the course. pic.twitter.com/yvb1C5ACRn
— PGA TOUR (@PGATOUR) April 6, 2019

Tony Finau was close to missing the cut, but finished with two consecutive birdies to stop an early exit.

Others were not so lucky.

Luke Donald and Billy Horschel struggled in their second rounds and missed the cut.