Second seed and defending champion Lleyton Hewitt [ Images ] was upset 6-3, 7-5 by Frenchman Julien Benneteau [ Images ] to cap a day of surprises at the Las Vegas [ Images ] Open on Wednesday.

Australian Hewitt, a three-times winner of the tournament, had reached the final in five of his six previous appearances in the event.

Fifth seed Potito Starace and number eight Nicolas Kiefer [ Images ] were also knocked out.

Benneteau, the world number 61, failed on his first attempt to serve out the match but broke Hewitt again and held to set up a clash with unseeded American Sam Querrey who needed less than an hour to eliminate Kiefer.

"It's a good win," Benneteau told reporters after reaching his second quarter-final of the year. "I'm very happy about this match and I hope to be fit like this in the quarter-final on Friday."

American qualifier Amer Delic set up a match against fourth seed Guillermo Canas [ Images ] of Argentina when Starace retired with a back injury after trailing 6-3, 3-0.

"It definitely feels good to get through for the first time," Delic, 25, said after reaching his first ATP quarter-final. "No better place to get lucky than in Vegas, I guess."

Querrey converted five of six break points to upset German Kiefer 6-3, 6-1.

"I played really well," the 20-year-old Californian said. "I started off a little sluggish but then just played solid and kept the ball to his forehand. I played aggressive, especially when I was returning his second serve."

Argentine Canas broke big-serving Australian Chris Guccione four times to win their second-round match 6-2, 7-5.

The 30-year-old from Buenos Aires held off a Guccione fightback in the second set to seal victory in just under an hour-and-a-half on the Stadium Court.

Serving for the match at 5-4, Canas saved three breakpoints before his towering left-handed opponent levelled at 5-5.

The Argentine, bidding for an eighth ATP title, then won the next two games to book a quarter-final clash with Delic.

"I feel great," Canas said. "Whenever you play a tough, big-serving player, it is always a danger but I feel very confident in my game. I am returning very well and I'm moving very well."