Third seed Murray failed to rise to the challenge of the in-form Swiss, who denied him a single break point in a brisk 6-4, 6-3, 6-2 defeat on Arthur Ashe Stadium at Flushing Meadows.
“At 5-4 in the first set, it was an important game and I had quite a few chances to close it out, but for the most part I didn’t create break point chances,” said Murray, who smashed his racket after dropping the first set.
“Everyone takes a little time to feel comfortable on court, but I didn’t think I was playing poorly. I would’ve liked to play better. There were a fair few long points, but I didn’t get into enough return games, which was disappointing.
“I thought he played great. I made a few mistakes but for the most part he hit a lot of lines, he hit big shots and he played too well. When it’s breezy conditions it’s difficult but I’ve had a good run the last couple of years and I played a bad match today.”
Wawrinka, the last man to beat Murray in the first week of a grand slam at the US Open in 2010, picked up where he left off against fifth seed Tomas Berdych to reach a first major semi-final.
“He [Murray] is the defending champion, he’s a tough opponent,” said the ninth seed. “I’m just really happy. It was a crazy match and to beat him was amazing.”