The British number two has only failed once in the last 32 when he was in the main draw and progressed to the fourth round 12 months ago.
Having lost just six matches to Jiri Vesely in the first round, Evans looked set for another comfortable afternoon against 30-year-old Duckworth when he took a two-set lead.
But Duckworth, ranked 83rd, took his first break point of the match in the ninth game of the third set, then had an early break in the fourth before Evans fought back to clinch a 6-3 6-2 4- 6 6-4. victory.
The 20th seed couldn’t hide his joy at the end, spreading his arms wide and running towards the net after taking his first match point with a backhand pass that landed on the line.
Evans will now face former champion Marin Cilic for a place in the last 16.
Meanwhile, Iga Swiatek put down a marker with a straight-set victory over former champion Sloane Stephens.
It seemed like a tricky draw for the world number one, who has struggled for form since ending her 37-match unbeaten streak at Wimbledon.
But they have been quiet so far at Flushing Meadows and secured a 6-3 6-2 win over Arthur Ashe Stadium.
The article is in French
. Dan Evans reserve clash third round with Marin Cilic lUS Open