Schwartzman, number 16 in the world ranking, triumphed 7-6(3), 7-5 and 7-6(6) against Popyrin, 84th in the world, in his first confrontation with the Australian on the ATP circuit.
The only precedent dates back to a Canberra 2016 challenger, in which the Argentine won 6-3 and 6-2.
On court 11 at Flushing Meadows, Schwartzman annulled four set points in the first set before forcing a tiebreaker and winning it with authority 7-3.
In the second set, the Argentine managed to overcome a break suffered in the first game and achieved another in the twelfth game to deal a blow to the match and frustrate his rival.
It was a physically and mentally demanding match, but Schwartzman managed to take the most delicate moments to his side. He annulled a new match point in the tiebreaker and won 8-6 to secure his place in the round.
A third-round duel awaits him against the winner of the match between the American Francis Tiafoe and the Australian Jason Kubler. EFE
Schwartzman defeats Popyrin and enters the third round
Diego Schwartzman Photo file: Secretary of Sports of Argentina Argentina.gov.ar CC BY 4.0