A friendly gallery helps Sahith Theegala in the U.S. Amateur at Riviera

Players in the early rounds of the U.S. Amateur golf championship might have a couple of friends, maybe their parents, walking the course with them, quietly urging them on. The atmosphere almost seems more like a weekend club tournament than the most prestigious amateur event in the world.

Sahith Theegala has more of a throng following him, maybe 15 vocal family members and a similar number of enthusiastic friends and teammates from Pepperdine, where he will be a junior in the fall.

Quiet? Hardly. When Theegala made a 25-foot, double-breaking birdie putt on the par-five 17th hole at Riviera Country Club on Wednesday, the response was instant and loud.

“After that fist pump on 17, how loud they got, I mean, that was awesome,” the 19-year-old from Chino Hills said. “That basically made my week right there.”

The putt tied his match against Gavin Hall, a 22-year-old who played for Texas and was competing in his fourth U.S. Amateur. Both bogeyed the 18th hole, but Theegala prevailed when he parred the first extra hole, the 501-yard par-four first, and Hall bogeyed.

Theegala, who reached the quarterfinals of the 2016 Amateur, made the cut in the PGA Tour’s Genesis Open at Riviera in February. The experience has paid off in the Amateur. He feels at ease on tee shots, aware of the trouble spots on the George Thomas-designed layout in Pacific Palisades.

“This is like my 10th time playing Riv, so the sight lines with my driver I’m really comfortable with,” he said. “Course knowledge is huge.”

As is the support.

“I was kind of doing it for them at the end,” he said.

Theegala will play Doug Ghim, who won the Pacific Coast Amateur last month, in the round of 32 Thursday morning. Winners will move on to the round of 16 in the afternoon.

Also Wednesday, the youngest player to reach match play, 16-year-old Ricky Castillo of Yorba Linda, took a lead on 21-year-old Edwin Yi of Los Angeles on the sixth hole and never lost it, winning 3-and-1. Castillo was the youngest player to play in the Amateur two years ago as a 14-year-old. Yi had played in three previous Amateurs. Castillo, 5-feet-11 and all of 125 pounds, made five birdies without a bogey.

“I was hoping I could make it to match play,” said Castillo, a junior at Valencia High in Placentia who has already committed to play at the University of Florida. He’ll play Connor Syme of Scotland on Thursday morning.

Syme ousted Maverick McNealy, the world’s top-ranked amateur in 2016 and No. 2 entering the Amateur, 2-and-1. McNealy was hoping for a better showing this week, in part to ensure a spot on the U.S. Walker Cup team, which will be named as early as Sunday. McNealy, who recently won the Ben Hogan Award as the nation’s top collegiate golfer after his senior year at Stanford, was a member of the 2015 U.S. team that was trounced by a team from Great Britain and Ireland in the biennial competition among amateur golfers.

The Walker Cup will be played at Los Angeles Country Club Sept. 9-10.

The No. 1 ranked amateur in the world, Joaquin Niemann of Chile, was beaten by Braden Thornberry of Mississippi, 2-up. Thornberry was the NCAA individual champion and tied for fourth at the PGA Tour’s FedEx St. Jude Classic.

Hayden Wood, who was medalist after playing two rounds of stroke play Monday and Tuesday in nine under par, defeated Chris Crisologo of Canada, 4-and-3. Crisologo was the last player to qualify in match play in an early-morning playoff involving 13 golfers for eight spots.

The tournament finishes on Sunday.