Auger-Aliassime quickly found himself down 4-1 in the first set, with Shelton making good use of the serve and volley, but he broke back as his opponent served for the set.
However, a poor service game gave the initiative – and the first game – to fifth-seeded Shelton.
Shelton had the only break point of the second set but Auger-Aliassime, increasingly confident, saved it, before clinching the tiebreaker on a wild double fault from Shelton.
A tight third set also came down to Shelton’s serve, with Auger-Aliassime converting his third match point.
“He played a lot better than me at the beginning,” Auger-Aliassime said.
“It was a weird start, but as the match went on I found ways to generate returns on the court.”
