On Tuesday evenings, Barbara M. Keenan--who yesterday became the first woman in Virginia to be sworn in as a circuit court judge--leaves her courtroom to play forward on a Fairfax County women's basketball team called the "Windsailers."

It's not coincidental that Keenan's basketball team is 6 and 1 and tied for first place in the county women's recreation basketball league, say her teammates and coach, Christopher Stokes. Keenan the basketball player, they say, is little different from Keenan the judge: she's a team player, but she plays to win.

"Barbara plays basketball like she practices law: fairly and competitively," said her teammate Barbara Mattick, a Fairfax lawyer. "I couldn't think of a better person to sit on the bench. She's a very intense player."

Keenan, 31, until yesterday a Fairfax County General District Court judge, was elevated to the circuit court in a controversial election that found her vying with Johanna L. Fitzpatrick of the county's juvenile and domestic relations court bench. Both were trying to become the first woman in Virginia to join the 113 males who sit on the state's circuit courts.

Legislators picked Keenan earlier this month to fill a vacancy created Dec. 17 when James C. Cacheris resigned from the $54,000-a-year circuit court post to become a federal district judge in Alexandria.

A quiet, lithe woman with shoulder-length brown hair and a penchant for country music, Keenan declines to discuss to her selection, her views on the criminal justice system or the Equal Rights Amendment, contending it would be improper for a judge to discuss those matters.

Keenan dismisses suggestions that her sex helped her win the position. "I don't feel that being a woman has stopped me from getting any job that I've ever aspired to," she said. "It's a matter of how hard you work. Of course, I think it would be great if there were more women on the bench, but as a woman I don't see the issues any differently."

Her up-by-the-bootstraps philosophy and love of sports have endeared Keenan to her colleagues in the conservative, mostly male Virginia judiciary. "We've always thought of Barbara as one of the boys," said Robert M. Hurst, chief judge of Fairfax's General District Court. "She has always been fun to be around. She's always had a drive and a more common-sense, realistic approach to things as opposed to an ethereal view."

Next week she begins her duties as the eleventh member of the Fairfax Circuit Court, the court which has jurisdiction over felonies and most civil lawsuits in Virginia.

Keenan was born in 1950 in Vienna, Austria, while her father served an Army tour there. She received a bachelor's degree in American history from Cornell University in Ithaca, N.Y., in 1971 and graduated from George Washington Law School in 1974.

She was an assistant commonwealth's attorney in Fairfax from 1974 to 1976, then went into private practice for three years before being appointed to the general district court in 1980. She is married to a lawyer, Lawrence Keenan, and lives in the county.