Three Americans - favorites Brian Gottfried and Bob Lutz and underdog John Whitlinger - reached the quarterfinals of the $100,000 Volvo Tennis Classic yesterday afternoon at George Washington University's Smith Center.

Gottfried, seeded No. 3 and the winner of two recent tournaments in the Colgate Grand Prix series, got his aggressive game grooved in the second set and ran over lefthander George Hardie, 6-4, 6-1.

Lutz, the No. 6 seed, never established the rhythm of his serve-and-volley game, but was far more self-assured on the big points that Chico Hagey, ranked only No. 57 in the U.S., and won, 6-4, 6-4.

Whitlinger, the 23-year-old former NCAA champion from Stanford who is ranked 43-d in the U.S., upset 1976 Australian Open champion Mark Edmondson, 6-2, 3-6, 7-5.

Whitlinger lost to Steve Docherty in the final qualifying round Sunday, but got into the draw as a "lucky loser," filling the vacancy created when fourth-seeded Roscoe Tanner pulled out with brochitis.

Docherty is long gone, having lost in the first round to Cliff Richey (also since departed), but Whitlinger plays Lutz tonight for a berth in the semi-finals.

Gottfried, winner of the Towson International and the American Airlines Tennis Games and runner-up to Bjorn Borg in the U.S. Indoor Championships in Memphis two weeks ago, has become a regular in the late rounds of tournaments the past six months.

"I like the habit. It's lot nicer that playing one match and practicing the rest of the week," said Gottfried, who has worked his way up diligently and is currently ranked No. 5 in the U.S. at age 25.

Gottfried let a couple of breack points escape in the first game and had his hands full the rest of the first set with Hardie, an aggressive former all-America from Southern Methodist University who last played Gottfried when he was at Trinity (Texas) Univeristy.

Gottfried broke for the first set in the 10th game, then came on in the second like a denizen of one of the alligator farms in his hometown of Fort Lauderdale.

From 1-1, Gottfried ran five straight games, conceding only five points. At one stage, he won 12 of 13 points and left Hardie muttering on the sidelines.

During the stretch of glorious shot-making by Gottfried, Hardie was reduced frequently to holding up his hand forlornly, acknowledging by word and gesture, "Nice shot."

Hardie went to the net and watched futilely as shots buzzed by him. When he had the passing shot covered, Gottfried lobbed him to death. When he stayed back at the baseline, uncertain territory for him, Gottfried exploded outright winners or took command of the net for decisive volleys.

"I hadn't played George in about six years," said Gottfried. "He's a lot better now, of course, but he still plays basically the same way he used to. He likes to attack, come in on everything. He's not real confident at the baseline, I felt I had a good chance to win the point."

In short, Hardie plays very much like Gottfried used to. But not anymore. Gottfried has the confidence to use all the weapons in his all-court arsenal these days, and is showing that his rise to No. 7 in the computerized world rankings of the Association of Tennis Professionals is no mistake.

Lutz was inconsistent and had trouble keeping his concentration riveted, but was never in trouble against the lanky Hagey, a former Stanford teammate of Whitlinger who was talent but little confidence.

"He made a lot of bad errors on crucial points," noted Lutz. "The first couple of points of a game he played pretty steady, but on the pressure points he was hitting the bottom of the net.

"I'm surprised he didn't come in more. He's got a good serve and backhand," added Lutz, 29, who had never seen his 23-year-old opponent play before.

Lutz served for the match at 5-3 in the second set, but was broken at 15, slipping and falling awkwardly on the break point as Hagey passed him with a cross-court backhand.

But typical of his performance, Hagey netted a backhand and forehand, both unforced, and popped a backhand volley long to fall promptly down, 0-40.

He saved one match point with a good serve, but then Lutz caught him with a perfect backhand topspin lob that kissed the baseline. Hagey could only grope it back, on the dead run with his back to the net, and Lutz put away an overhead for the match.

Whitlinger was down, 0-2, in the final set, but leveled at 2-2 and then broked Edmondson for the match.

This was a victory of a backcourt player over one who likes to serve and come in as often as possible. Whitlinger scrambled well, and Edmondson missed too many volleys in the end.

In the final game, Edmondson punched a backhand volley long and then was passed with a backhand, down-the-line return winner.

Whitlinger knocked a backhand a mile long to make it 15-30, but then his hard forehand forced a low forehand volley error that made it 15-40 match point.

Edmondson, his horseshoe moustache acceptuating a woeful countenance, sailed a backhand long, and Whitlinger was in the quarterfinals of a tournament for the first time since November.