One year ago, Hana Mandlikova was convinced she could challenge for the No. 1 ranking in women's tennis. And tournament victories in Brisbane, the Australian Open and the Virginia Slims of Washington, all before the end of February, had convinced many others.

But injuries in the spring sidelined Mandlikova for more than two months, preventing her from seriously competing with Martina Navratilova and Steffi Graf for the top spot. Now, after what she calls the most strenuous training of her career, Mandlikova finds herself here again, trying to defend her Virginia Slims of Washington title and trying to regain the form that has kept her among the top five in the world for most of her career.

Yesterday, Mandlikova put together some impressive stretches of tennis at the Patriot Center to beat frequent doubles partner Wendy Turnbull, 6-3, 6-2, to advance to the second round of the $300,000 tournament.

In other matches, played on the George Mason University campus, seventh-seeded Barbara Potter eliminated Leila Meskhi of the Soviet Union, 7-6 (7-4), 6-0, to move into the quarterfinals. But two other Soviet players remained alive in the competition.

Rapidly improving Natalia Zvereva, 16, the No. 8 seed, also advanced to the quarterfinals, by beating Robin White, 6-4, 6-2. And Larisa Savchenko, the third Soviet player, beat Barbara Gerken, 6-1, 6-3.

Last night, second-seeded Pam Shriver defeated Sylvia Hanika while Gabriela Sabatini, the No. 3 seed and the fifth-ranked player in the world, overpowered promising 14-year-old Kim Kessaris, 6-3, 6-1.

Shriver, the No. 4 player in the world, had a much easier time than she could have imagined, rolling over Hanika, 6-2, 6-0.

Shriver kept serving wide to the left-handed Hanika, setting up easy volley situations. Hanika, on the other hand, struggled with everything from her serves to simple volleys. "She obviously wasn't at the top of her game," Shriver said.

But the top match in the afternoon session was the one between Turnbull and Mandlikova, the sixth-ranked player in the world.

Turnbull broke Mandlikova's serve twice in the first set, but couldn't serve well enough to dictate the terms of the match as she had in two recent meetings, both of which she won.

After falling behind, 1-0 and 2-1, at the start of the match, Mandlikova was able to break back each time to tie the set. Mandlikova finally held serve to go ahead, 3-2, then broke Turnbull again for 4-2 en route to a first-set victory.

Turnbull kept mixing the pace in the second set, sometimes coming in to volley even on Mandlikova's serve. "It's something Wendy does against everybody, not just me," Mandlikova said. "She's not as fast as she was three or four years ago, but she's so smart and she was trying to keep me from getting into a rhythm."

Turnbull was successful at that for awhile, hitting some decisive volleys to get within 3-2. But an error-filled game that could have gone to either player went to Mandlikova after many deuce points for a 4-2 lead.

Mandlikova used a couple of her own deft volleys to break serve and go up, 5-2, before closing out the match by holding serve at love.

"Hana was a little erratic. She missed quite a few first serves," Turnbull said. "But I was erratic, too. I'd hate to see the percentages of first serves. I didn't hit enough first serves to get me flowing.

"The last two times we played I beat her, but today I couldn't capitalize on what I know. No, I can't tell you what that is," Turnbull said, smiling.

While Turnbull, 35, a holder of nine Grand Slam titles, said this could be her last year of competition, Mandlikova just turned 26 and figures she still has a good run at the top spot.

An injured right foot and sprained ligaments in her back and thigh ruined Mandlikova's 1987 season, if you can call a record of 50-13 "ruined."

Mandlikova hasn't started this year the way she did last, but a quarterfinal loss to top-ranked Graf in the Australian Open and a quarterfinal loss to Savchenko, with a tie-breaker in the third set, aren't anything to be discouraged about for a player coming off such injuries.

Asked how long it will take to get her form back, Mandlikova said, "I think I was in form last week, but I was unlucky. When I couldn't play for 2 1/2 months last year because of the injuries, it got very discouraging. Very tough. I was playing well, . . . then got injured."

Potter, also a winner yesterday, got off to a disturbing start when George Mason police made her wait 30 minutes while writing a ticket for making an illegal left turn on campus. That might have had something to do with her poor serving, and narrow first-set victory over Meskhi. Potter's serve was broken three times in the first set.

"I was pretty perturbed," Potter said. "I couldn't keep my {serve} toss in the same solar system. I had some really, really bad double faults. It was kind of amusing, but it wouldn't have been if I had been playing someone who could hold serve somewhat routinely."

YESTERDAY'S RESULTS SINGLES First round

Gabriela Sabatini (3), Argentina, def. Kim Kessaris, Hendersonville, N.C., 6-3, 6-1; Hana Mandlikova (4), Australia, def. Wendy Turnbull, Deerfield Beach, Fla., 6-3, 6-2; Larisa Savchenko, Soviet Union, def. Barbara Gerken, Thousand Oaks, Calif., 6-1, 6-3. Second round

Natalia Zvereva (8), Soviet Union, def. Robin White, San Jose, Calif., 6-4, 6-2; Barbara Potter (7), Woodbury, Conn., def. Leila Meskhi, Soviet Union, 7-6 (7-4), 6-0; Pam Shriver (2), Lutherville, Md., def. Sylvia Hanika, West Germany, 6-2, 6-0. DOUBLES First round

Elise Burgin, Baltimore-Robin White, San Jose, Calif. (4), def. Isabelle Demongeot-Nathalie Tauziat, France, 6-3, 6-4; Nicole Provis, Australia-Judith Wiesner, Austria, def. Jennifer Goodling, York, Pa.-Jeri Ingram, Silver Spring, Md., 6-1, 6-1.

TODAY'S SCHEDULE In order of play MORNING MATCHES (10 a.m.)

Helena Sukova (5) vs. Larisa Savchenko; Hana Mandlikova (4) vs. Terry Phelps; Nathalie Tauziat vs. Gabriela Sabatini (3); Larisa Savchenko-Natalia Zvereva vs. Eva Pfaff-Wendy Turnbull; Natalia Bykova-Leila Meskhi vs. Terry Phelps-Stephanie Rehe. EVENING MATCHES (6:30 p.m.)

Martina Navratilova (1) vs. Gigi Fernandez; Jeri Ingram vs. Zina Garrison (6); Martina Navratilova-Pam Shriver (1) vs. Ann Henricksson-Wendy White.

TUESDAY'S LATE RESULTS FIRST ROUND SINGLES

Martina Navratilova (1), Fort Worth, def. Judith Wiesner, Austria, 6-2, 6-3. DOUBLES

Mary Lou Daniels, Chicago-Anna Maria Fernandez, Torrance, Calif., def. Zina Garrison, Houston-Gigi Fernandez, Miami (3), 6-4, 2-6, 6-2.