U.S. green card restrictions have forced Cam Davis out of next week's Open Championship.

Davis, whose first PGA Tour win came at the Rocket Mortgage Classic last weekend, was listed as an alternate for the year's final major and on Thursday that standing granted him a spot in the field.

Kevin Na withdrew due to travel restrictions, but the R&A announced that Na's place will be filled by two-time Major winner Martin Kaymer instead of Davis.

After his opening round 4-under 67 at the John Deere Classic overnight, Davis told Australian Golf Digest why he is unable to travel.

"Yeah, I got married last year in September and decided to start the green card process to make travelling in and out of the country so much easier," Davis said.

"But, unfortunately, for six months I'm not going to be able to leave the States while that's getting processed. That means I'm not able to go next week."

It would have been Davis' second appearance at the Open Championship after his T39 finish in 2018.