"We knew there was already another gymnastics event in town this weekend. And it was being put on by a really good friend," said Pat Darr, director of events at Capital Centre. "We certainly didn't want to hurt him, but this is business. We couldn't pass up a deal like this one."

It is but one small measure of the growing popularity of gymnastics in America that within a span of less than 24 hours -- and quite by accident -- the Washington are will be the site of two major gymnastics events, bringing an unuaual concentration of American and European gymnastics talent to the national capital.

While most of the nation's sports attention will be directed toward Philadelphia and the final rounds of the NCAA basketball tournment this weekend, the small but burgeoning community of gymnastics fans will be drawn to George Washington University's Smith Center tonight at 7 for the Capital Gymnastics Invitational competition, featuring six of the nation's top-ranked female gymnasts.

Saturday, at 2 p.m., the focus will shift to Capital Centre and Nadia Comaneci's gymnastics road show, Nadia 81.

Can the Washington area support such a surfeit of gymnastics in so short a time?

Promoters of both events, not surprisingly, say yes, but they agree the timing has been less than ideal. For one thing, the fans keep confusing the events. They call Capital Centre for tickets to the Capital Invitational and the Capital Invitational for tickets to Nadia 81.

"There has been some confusion about which event was which," said Bob Geogham, promoter of the Capital Invitational and also promoter of the Capital Classic basketball game last night at Capital Centre. "We're promoting all American girls, and their thing is promoting Romanian gymnasts. I suppose it may hurt us a bit, but I think we'll be all right. There are a certain amount of people who would want to go out and see Nadia and there are a certain amount of people who would want to come and see the the American girls."

Some months ago, when he settled on March 27 as the date for the Capital Invitational, Geoghan had no idea that Nadia 81 would be in town the next day. Neither did anyone else. Things were going along smoothly, and he was even contemplating using Capital Centre ticket distribution apparatus, Geoghan recalled, until that telephone call from Darr.

"Bob, I wanted to be the first to tell you. We're not trying to hurt you, but . . ."

As Darr recalls it, there had been discussions earlier in the winter with the promoters of Nadia 81 about including Capital Centre on the American tour, but no mutually acceptable date could be found. Nadia 81 went off to Venezuela, and the plan was scratched.

Then while in Canada on a business trip, Darr received a second telephone call. There was one possibility after returning from Venezuela. What about Saturday, March 28?

"I told them it would have to be in the afternoon," Darr said, "because we had a Bullets game that night."

So the deal was made. Costarring with American Kurt Thomas, Comaneci, winner of seven markes of 10 and three gold medals, two silver and one bronze at the age of 14 in the Montreal Olympics, will bring her gymnastics exhibition to the Capital Centre.

Tonight at Smith Center, Shari Mann, 15, of Potomac, a student at Montgomery County's Winston Churchill High School, will defend the title she won a year ago by five-hundredths of a point over Lisa Keis of Cheektowaga, N.Y.

Her competition will include 1980 U.S. Olympians Tracee Talavers, 15, of Walnut Grove, Calif.; Kathy Johnson, 21, of Atlanta Julianne McNamara, 15, of Danville, Calif., and Zeis.

"It's going to be real close," said Mann, working out in the practice room yesterday at the Smith Center. "I'll try to hit all my events real tight and solid."

Chewing bubble gum in the corner, Talavera, the top-ranked woman gymnast in the U.S., was taking everything in stride. "I don't know what I do. I just get out there and do it," she said.

Also competing will be Tammy Smith, 14, of Westminster, Md., winner of several national gymnastic competitions but not yet eligible for international competition because of her age.