Sam Querrey has been a fixture in the ATP World Tour's top 100 for more than a decade.

But the laid-back Californian has always seemed to be slightly less than the sum of his sometimes extraordinary parts. Last summer, he offered a glimpse of what could be, beating No. 1-ranking Novak Djokovic in the third round at Wimbledon. But no one was quite prepared -- including Querrey himself -- for what happened last week on the scary-fast blue courts of Acapulco, Mexico.

The 29-year-old's serve and forehand were consistently lethal, the decision-making and movement decisive and unwavering. And that backhand? Where did that flat, fully committed stroke come from?

Querrey defeated four top-20 players in succession to win the Abierto Mexicano Telcel title late Saturday night in Acapulco. The last obstacle, in a stunning final result, was No. 6-ranked Rafael Nadal, 6-3, 7-6 (3).

Sam Querrey won his ninth career title -- and certainly his biggest -- with a stunning win against Rafael Nadal in Mexico. REUTERS/Henry Romero

Less than an hour after the signature win of his career, Querrey was still trying to make sense of it all.

"I don't know," he told ESPN.com over the phone, sounding genuinely baffled. "I almost got to that mentality of 'Screw it; I'm going to hit every ball as hard as I can and see what happens.' Even on break point, if I missed it I was going on to the next point and thinking the exact same way."

That, tennis fans, is called confidence.

Nadal, who has struggled with that fleeting commodity, was impressed.

"He played very well, almost reaching perfection," Rafa said afterward. "I played under a lot of pressure because of his serve and baseline game. He left me with very few options, and the few I had he also played good."

Nadal knows something about perfection. Before the final, he had gone a perfect 14-0 in Acapulco, winning each of the 28 sets he played. And, he was 4-0 against Querrey going in.

Hard to believe that after beating Djokovic, Querrey had gone 0-7 against top-20 players before reaching Acapulco, where he was a semifinalist a year ago. This tournament, the lead-in for Indian Wells, featured no fewer than five of the ATP's top-10 players, as well as 2009 US Open champion Juan Martin del Potro.

Querrey won his second ATP World Tour 500 championship, bookending his triumph seven years ago in Memphis. Querrey became the first American to win an tournament at this level title since Andy Roddick took Memphis in 2011 -- and the first American to win this tournament in all of its 24 years.

Here, in order, is the list of Querrey's casualties: No. 45 Kyle Edmund 6-2, 4-6, 6-3, No. 11 David Goffin 6-2, 6-3, No. 9 Dominic Thiem 6-1, 7-5, No. 17 Nick Kyrgios 3-6, 6-1, 7-5 and No. 6 Rafael Nadal 6-3, 7-6 (3). Note that one dropped set against those top-20 players.

"I knew I was capable of it," Querrey said. "The Goffin match gave me some confidence. It helped me commit to being 100 percent aggressive."

Querrey entered the tournament No. 40 among ATP World Tour players. He will rise to No. 26 when the rankings are released Monday. That will make him the No. 3 American man, not far behind Jack Sock and John Isner.

The key to the best tennis week of his life was his serve. Querrey served impeccably, with 19 aces, and he saved all six break points. He also led the tournament with 17 breaks of serve, converting 17 of 28 break points (61 percent) overall.

Yes, he served huge, but that backhand was so good it was almost laughable.

"I know, I know," Querrey said in disbelief. "That's the first time I've really committed to it. I'd get a short ball and rip it down the line or go crosscourt more than I usually do. The more I did it, the more comfortable it got.

"This game is all about confidence, and I think I found it this week."

When Querrey beat Djokovic at the All England Club, it ended a 30-match winning streak. But ultimately Querrey's quarterfinal run at Wimbledon was leavened by first-round exits at the other three Grand Slams.

In January's Australian Open, Querry won two matches before falling to No. 1-ranked Andy Murray. He won two more matches recently in Delray Beach, but lost in two tight sets to del Potro.

Querrey credited his coach Craig Boynton with driving home this message: "Even if you miss it, keep firing. Do it again. And again."

Stan Wawrinka won his first major at the age of 28 -- and he has won two more after hitting 30. Angelique Kerber broke through with two major wins last year at the age of 28. Querrey, who turns 30 in October, said he was uncharacteristically nervous before the match.

"But after every [service] hold, I gained a little more belief," he said. "I played a great game to break him and in the second set the closer we got to the tiebreaker, I know there was more and more pressure on him.

"I was really focused on being aggressive. I'll remember this for the rest of my life. Beating these players here gives me a ton of belief that I can do it more often."