LOS ANGELES — No one ever said the learning curve was one smooth, flowing line.

Sam Querrey has hit one of the bumps in that curve. It's a new experience, and he's not enjoying it a whole lot.

"I've been struggling a bit lately," says Querrey, the 19-year-old rising tennis star from Thousand Oaks in just his second season on the ATP tour. "I haven't won a lot of matches — zero — in my last six tournaments."

The numbers are, indeed, both unfortunate and unfamiliar for Querrey.

After rising like a rocket in his first season as a pro — the ATP media guide notes he climbed more than 600 places in the rankings, finishing the year at No. 127.

This year, the ascent continued as Querrey broke into the top 100 and kept going, reaching No. 66.

Then he hit that speed bump. After falling to Mardy Fish in the first round of last week's Countrywide Classic at UCLA, Querrey has lost nine of his last 10 matches, and is currently ranked No. 91.

"I've never experienced this before where I've lost six times in a row," Querrey says. "In every aspect of your life — if you're a businessman, if you're an athlete — you have your ups and your downs. This is just a little downhill slide, but I'm going to overcome it."

Being interested only in results, Querrey isn't too interested in dwelling on mitigating factors, but it should be noted that he hasn't been losing to guys who just wandered onto the court after buying a racquet at a thrift store.

The nine-loss stretch began with a second-round defeat in Miami against one Roger Federer. Even if you follow tennis about as closely as a vegan tracks beef prices, you're probably aware he's the world's top-ranked player. Others who have defeated Querrey of late are ninth-ranked James Blake and No. 11 Tommy Haas; seven of the nine losses are to players ranked higher than Querrey, which means that, statistically at least, they don't qualify as upsets.

Additionally, the eight matches before the UCLA tournament were played on clay (six) or grass (two) — not exactly the surfaces of choice for someone who grew up on the hard courts of Southern California. It's still tennis, of course, but it's not quite the same. Anyone who's ever sat down at an Internet café outside of the English-speaking world can probably identify with the feeling — the computers still run Windows, but everything is just a little different, and even the most basic activity is suddenly a little more difficult.

"It was tough for me for the first time, going from the clay to the grass," Querrey admits. "But it's just something I'll get used to. I like playing on both surfaces, and I'm going to get used to it."

Those surfaces are behind him now, and the reality of his current standing on the tour is that he's generally going to meet those highly ranked players pretty early in the draw. To move up, he's going to have to find ways to knock them off.

This is where the mental side of the game comes in, and it's a big focus for Querrey. Three of his recent losses came after he won the first set; in two others, he lost first-set tiebreakers that might have changed the tenor of the match. That alone is enough to make his current frustration understandable.

"On break points or bigger points, I need to be a little bit more aggressive and try to win the points," he says. "I'm kind of playing not to lose, hoping the other guy's going to miss.

"So that's one of the things I really want to work on, which unfortunately is really something you can only do in a match."

But he's also looking for answers off the court, reading and listening to tapes that deal with the mental aspect of winning. There's no one person he's turning to for advice, he says: "I kind of dabble with everyone."

Which is a good thing, because as he deals with this flat spot in the learning curve, there's no shortage of people willing to offer advice: His mom. His friends. The members of his "Sam's Club" rooting section. "Yeah, they're giving me their opinion," he says, laughing.

Querrey finds reasons to laugh and smile through all of this discussion, so it's clear he's far from beat down by the current state of affairs. And one way he's trying to address it is by adjusting his schedule. Between this week's tournament in Indianapolis and the mid-August event in Cincinnati — his last stop before the U.S. Open — he'll detour to the Vancouver Open. That's a Challenger-level event — the type that feeds the big ATP tournaments — and Querrey had great success building his professional résumé at Challengers a year ago.

"I haven't had that much success on the tour the last six or seven weeks, so I'm hoping to go back to a Challenger and hopefully win it," he says. " It can't hurt."

Neither can Querrey's perspective, really. He may not have enjoyed the last six tournaments, but he understands this is part of the professional tennis life, part of gaining the experience that only comes with time.

"Exactly," he says. "If I just keep doing the right thing, working hard, doing what I can do, I think it will turn around."

Querrey and his fans have no reason to believe it won't happen.

Of course, if things turn this week in Indianapolis, so much the better.

— Contact columnist David Lassen at dlassen@VenturaCountyStar.com.