It didn't take long before upsets were witnessed at the U.S. Open. The biggest of the afternoon sessions was clearly, qualifier Daniel Evans of Great Britain defeating 11th seed Kei Nishikori, 6-4, 6-4, 6-2.

Nishikori double faulted 8 times and sprayed 38 unforced errors and Evans was able to capitalize breaking 6 of his 9 opportunities.

Nishikori is the highest ranked Asian player and admitted after the match, that he had never seen Evans play. He had no answer for the 179th ranked player in the World who played aggressively and with a purpose on Monday.

Evans had to win 3 qualifying matches to enter the tournament and has mainly played Challenger events throughout 2012. He will face Bernard Tomic next.

In a couple of mild upsets on Monday in the Men's bracket, Ivan Dodig of Croatia defeated Fernando Verdasco 6-3, 7-5, 1-6, 4-6, 6-3. Also, Andreas Haider-Maurer defeated  30th seeded Ernests Gulbis in 5 sets, 3-6, 6-3, 1-6, 7-6, 6-4.

Gulbis and Verdasco had played well recently in U.S. Open Series events.

In the Women's draw, it is difficult to consider Venus WIlliams defeating Kirsten Flipkens an upset. But Williams knocked out the 12th seed in impressive fashion, 6-1, 6-2.

Patricia Mayr-Achleitner upset 29th seeded Magdalena Rybarikova 7-6, 6-3 in the day session.