The long-hitting South African will make his second U.S. Open start after posting 9-under-par 135 in final qualifying on May 16 at Walton Heath Golf Club. He turned professional in 2019 after representing his home country in the 2018 World Amateur Team Championship. Nienaber registered his first professional victory at the 2021 Dimension Data Pro-Am, a Sunshine Tour event that is also co-sanctioned by the European Challenge Tour. He beat Henric Sturehed in a playoff. In 2019, he captured the South African Amateur.