FLUSHING MEADOWS, NY — American men have usually been on the wrong end of upsets at the U.S. Open during the past decade. But Sam Querrey at least temporarily reversed that trend when the Thousand Oaks, CA native knocked off No. 14 Ivo Karlovic, 7-6 (5), 7-6 (5), 6-2, at Louis Armstrong Stadium Saturday afternoon.

Querrey advanced to the fourth round of a Grand Slam for the first time in his career. As a reward, the 20-year-old earned the right to face the top ranked player on the planet in No. 1 Rafael Nadal, who has already won the French Open and Wimbledon and is trying to end his season with a third major this year.

Querrey set goals for himself when the year started. Before September starts, he already needs to raise the bar.

“I wanted to win an ATP event and I wanted to get my ranking into the 30s,” he said. “I won the Vegas event in March and my ranking was 38 in May, so I accomplished both of those. My real goal now is to end the year in the top 32. I’d love to be seeded at the Australian Open next year. That’s the goal I set for myself.”

Two years ago, Querrey faced Nadal and lost. Both players said they have improved exponentially since that meeting. Nadal is now a four-time champion at Roland Garros and the reigning title holder on the grass surface. Meanwhile, Querrey is also in position to make his first quarterfinals appearance if he could record a second straight upset over a seeded opponent.

“A lot of things have changed the last two years,” said Nadal, who beat his upcoming challenger 6-7 6-2 6-3 in 2006 in 2006 and owns 31 titles compared to Querrey’s zero. “He wasn’t playing a lot [then]. Right now, he’s a very good player with big potential and big serves. It’s going to be a very tough match.

“I know I have to play very well if I want to win.”

Querrey entered the tournament ranked 55th in the world and said he’s improved since that meeting, becoming sharper mentally as well as physically.

“I’m learning about myself and how I like to warm up and what routine I like before matches,” he said. “My backhand is 10 times better. My transition game—coming to the net and beginning aggressive— is better than it used to be. It’s starting to show in my matches.

“I would sometimes let my mind wander for a game or two, and against these guys, if you do that, it could be a set. So I’m much more consistent and level-headed.”

At 6-6, Querrey enjoys a height advantage over most opponents. Against the 6-10 Karlovic, he was in the unusual role of vertically challenged underdog. Querrey surrendered just three break points and Karlovic didn’t convert on any. The Croatian is still looking to make his first fourth-round appearance at a U.S. Open.

Nadal took care of his business later in the day session, defeating Viktor Troicki in straight sets. The Spaniard’s only tense moments in his 6-4, 6-3, 6-0 win came in the second set when Troicki took a 3-1 lead. With many of the U.S. Open’s single-session record crowd of 37,380 packing the venue, Nadal roared back by winning 11 consecutive games. The 22-year-old advanced past the third round in the Open for the third time in his career.

“I am starting to play better,” Nadal said. “I started playing and serving well today. I was practicing much better yesterday than in the beginning days. So, that gives me more confidence. I think I am ready to play a good match in the fourth round. I know I have to play a good match if I want to win.”