De Minaur needed just one hour and 33 minutes to reach the quarter-finals, although the Australian eighth seed was far from flawless against the world number 435.
Breaks apiece early in the first set suggested the crowd on Louis Armstrong Stadium were about to enjoy a close contest, but Riedi’s all-or-nothing aggressive game proved his downfall.
The 23-year-old faced seven break points in the first set alone, allowing De Minaur to sweep up in 32 minutes.
De Minaur set out his stall for the second set by breaking from 0-40 down and winning five straight games before Riedi enjoyed a brief resurgence.
The Australian made just 55% of his first serves in the second set, but felt little pressure as Riedi made 15 unforced errors.
Riedi did remarkably well to reach the last 16 after two separate operations at the end of last year, but a leg issue began to hamper him in the final set and his service game fell apart.
De Minaur picked up his level from the second set to reach a Grand Slam quarter-final for the sixth time in his career.
