And there are two more U.S. women still waiting to play first-round matches Tuesday, including 13-time major champion Serena Williams.

It’s quite a change from recent times. In five of the previous seven years, including 2011, only four American women managed to make it out of the first round at Roland Garros, where they can be flummoxed by the slow, red clay that Europeans and South Americans know better.

“A couple years ago, everyone was asking me the opposite questions, on why American tennis was so bad. I told them, ‘I think we have some great young players coming up; it’s just the WTA right now has a lot of depth,’” said Bethanie Mattek-Sands, who eliminated 12th-seeded Sabine Lisicki of Germany 6-4, 6-3 on Monday.

“It really shows that some of the Americans are coming through, playing tough, grinding it out here on the clay,” added Mattek-Sands, who is based in Phoenix. “And it’s awesome.”

Lauren Davis, an 18-year-old qualifier from Boca Raton, Fla., surprised 30th-seeded Mona Barthel of Germany 6-1, 6-1 on Monday, when all six U.S. women who played were winners.

The others: Vania King beat Galina Voskoboeva of Kazakhstan 6-4, 6-2; Sloane Stephens defeated Ekaterina Makarova of Russia 6-4, 7-6 (6); Varvara Lepchenko beat Ksenia Pervak of Kazakhstan 6-2, 6-7 (6), 6-4; and Christina McHale edged Kiki Bertens of the Netherlands 2-6, 6-4, 6-4.

“We’re all pushing each other at the same time,” said McHale, a 20-year-old from Englewood Cliffs, N.J. “It’s like a healthy competitiveness, I think.”

Venus Williams, Melanie Oudin, Irina Falconi and Alexa Glatch won Sunday.

For Davis, it was her first victory in three career Grand Slam matches. She played cleanly, making only 11 unforced errors. Barthel had 44, including 12 double-faults.

The 5-foot-2 Davis finished last season ranked 319th, and she entered this week 162nd.

The secret to success against Barthel?

“Her backhand is so sick, so I tried to keep it away from her backhand more … and just kind of grind,” Davis said.

Now she faces McHale, and Mattek-Sands meets Stephens.

“I was just talking to Christina in the locker room. I’m like, ‘Who do you play?’ She’s like, ‘I play Lauren Davis.’ I’m like, ‘Oh, my God. I play Bethanie.’ So all the Americans are playing Americans, but it’s good that we’ll have people in the third round,” said Stephens, a 19-year-old from Coral Springs, Fla., whose late father, John M. Stephens, was the 1988 NFL Offensive Rookie of the Year.

“Everyone always says that we’re not good on clay,” Stephens said. “That’ll prove ‘em wrong.”

Last year, King and Mattek-Sands both reached the French Open’s third round. But no U.S. woman other than a Williams sister has made it as far as the fourth round since 2005.

“Usually, Americans are known to be bad on clay, because we don’t play a lot on clay. … Personally, I hated clay for so long — up until, like, three years ago,” said King, who splits time between California and Florida. “It’s a different movement with sliding, and different preparation. On hard courts, you have to play the points quicker, and on clay, you have to be a little bit more patient and work the points more.”

King’s best advice?

“You can’t go on the court thinking, ‘I hate this surface and I don’t want to be here,’ because then you’re going to play badly,” she said.

Mattek-Sands had been limited to a total of nine main-draw singles matches before Monday because of lower back and hip injuries. Her ranking slid from a career-high 30th last July to 167th this week.

“I like the clay, believe it or not,” Mattek-Sands said. “I feel comfortable on this surface.”

Then, as if sounding a note of caution to herself — and anyone else who might get too excited about the Americans’ early success in Paris this year — Mattek-Sands added: “It’s still only one round, though. There are a few to go.”

Didn’t always used to be such a big deal for U.S. women to win a match at the French Open. Hard to believe, maybe, but the WTA said 31 Americans reached the second round in 1982.