The Argentina Davis Cup star enjoyed his finest run in a grand slam tournament, surprising fifth seed Marin Cilic along the way.
Seeded 29 at Flushing Meadows, Schwartzman had no answer to the consistency of Carreno Busta who triumphed 6-4, 6-4, 6-2 in the last eight contest at the Arthur Ashe Stadium.
One of the smallest players on the circuit, Schwartzman, who stands at 5ft 7", captured the hearts of the American supporters with his big-hearted performances.
Schwartzman, 25, can look back proudly on a series of fine performances in New York - it was the first time he had passed the third round of any grand slam event.
Carreno Busta praised Schwartzman, saying: “I tried to be focused all the time. Diego is a fighter. You need to be focused, play aggressive and try to dominate the points. If you don’t, Diego will beat you for sure.”