Sam Ryder has birdied six of his final seven holes to shoot a bogey-free, 9-under-par 63 for the first-round lead at the Valero Texas Open.

Ryder was tied for the lead with Keith Mitchell (64) when he stepped to the tee at the par-5, 18th hole at TPC San Antonio's Oaks Course on Thursday.

He stopped his third shot about a foot from the hole and tapped in for the go-ahead birdie.

Mitchell is alone in second, while Brian Harman is third after a 6-under 66. Jordan Spieth is tied with Carson Young at 5-under 67.

Ryder, 35, has never won on the PGA Tour and holds the No.154 world ranking. If he wins the tournament, he would earn an invitation to the Masters next week.

"I've been focused ... I feel like my game's been in a good place and I've been generally healthy so I feel like I know kind of my DNA as a player and I've been able to just kind of hone in on that," Ryder said.

"The putter's been good this year, I think that contributes to my consistency."

However, Ryder was not 100 per cent healthy entering the tournament. He revealed that he strained his upper back or neck during practice Tuesday and had to skip the Wednesday pro-am.

Mitchell's round was also bogey-free and featured an eagle at the par-5 eighth.

"My game's been trending," Mitchell said. "I'd like to put some solid rounds together, hopefully it's this week.

"I feel like my scores have been showing at least in the first couple rounds lately that my game's where it needs to be and just going to try to stack 'em all up this week."

After an opening bogey, Spieth made two birdies on the front nine and four more on his way in, including one at the par-4 17th. After badly missing the fairway to the right and landing in a native area, he pitched onto the green and sank a 12-foot birdie putt.

A Texas native, Spieth won this event in 2021 and is looking for his first win on tour in almost three years. He has had a fine start to the season after recovering from off season wrist surgery.

"It's been a little bit of a mixed bag, but I've had way more (positive) days than I have in the last couple years, really since May of '23 when I first injured my wrist," Spieth said.

Other notable players tuning up for next week's major include Englishman Tommy Fleetwood (68), Sam Burns and Tony Finau (69) and Patrick Cantlay, Keegan Bradley and Swede Ludvig Aberg (71).

Rickie Fowler (75), Max Homa (76), Englishman Matt Fitzpatrick (76) and South Korea's Tom Kim (77) are in danger of missing Friday's 36-hole cut.

Defending champion Akshay Bhatia opened with a 74.