Popyrin, backed by a healthy pro-Australian crowd on John Cain Arena, started brightly before the Florida Gators product Shelton took control of the match, dictating points from the baseline with the help of a massive serve.
In a second set tiebreak, Shelton raced to a 4-1 lead before Popyrin clawed his way back to 4-5. However Shelton, a left-hander, steadied to take the set and the wind out of the sails of the parochial crowd.
From there, the American sailed through his service games, and broke the Australian in the 10th game of the set, winning 6-3, 7-6(4) 6-4.
This year’s Australian Open is Shelton’s first major tournament outside the United States, having played on on the college circuit for a number of years.
In his on-court interview following the win, Shelton said he was happy with his level of aggression — at one point he pulled out a 197km/h second serve — and said silencing the crowd was key to building momentum.
“I know I came from college tennis and I thought it was rowdy there, but this stadium is something special,” he said of John Cain Arena.
“I know that you guys were going for your hometown boy and I didn’t have most of the crowd, but thanks to everyone out there supporting me. It was great fun to be out on court.”
Shelton will face fellow American J.J. Wolf in the fourth round on Monday.