The 30-year-old Spaniard went down 2-6 6-1 6-4 6-2 to the defending champion at Flushing Meadows on Sunday.
"Every match is different," he is quoted as saying by Reuters. "Every day is different. Today Djokovic played better than me."
However, Ferrer added that he is pleased with his performance at the tournament.
"Of course, I am very positive," he said. "I reached the semi-final in a Grand Slam, my second time in a semi-final here at the US Open.
"I am very happy with myself and with my performance."
Ferrer has yet to reach his first Grand Slam men's singles final.