Ben Shelton Knocks Stan Wawrinka Out of ATP 500 Tournament in Basel

American youngster Ben Shelton continued his impressive run of form on Thursday, defeating three-time Grand Slam champion Stan Wawrinka in the second round of the ATP 500 tournament in Basel.

Shelton, 20, won 6-4, 6-3 against the Swiss veteran, who was playing in his first tournament since March due to a foot injury.

Shelton, who is ranked 120th in the world, broke Wawrinka's serve twice in the first set and once in the second set to secure the victory in 72 minutes.

The American has now won nine of his last ten matches and will face either top seed Casper Ruud or qualifier Marc-Andrea Huesler in the quarter-finals.

Wawrinka, 37, was making his comeback after undergoing two surgeries on his left foot earlier this year.

The former world number three, who won the Australian Open in 2014, the French Open in 2015, and the US Open in 2016, looked rusty at times but showed glimpses of his old form.

Wawrinka said after the match that he was pleased with his performance, considering his lack of match practice.

"I think it was a good match," Wawrinka said. "I'm happy with the way I played. I think I played well for a first match back."

"I'm just going to keep working hard and try to get back to my best level," Wawrinka added.