Ivan Lendl of Czechoslovakia got Roscoe Tanner for his birthday last night. Lendl, the seventh seeded player in the $125,000 Volvo Tennis Classic, celebrated his 20th birthday by defeating top-seeded Tanner, the defending champion, 6-4, 6-4.

There was a chocolate cake waiting for Lendl at courtside when the match ended at 11:50. But Lendl said it was too late to celebrate. "It was a good celebration on the court," he said. "I don't make mistakes; I win."

During the week, some cynics insisted that the tournament should be called the "No Name Classic" because of the lack of big name players. Last night, the tournament earned that name: the top two seed lost to "no-names" Lendl and Victor Amaya. But the name for the caliber of play was excellent.

Amays knocked out second-seeded Harold Solomon, 4-6, 6-3, 6-3.

The Lendl-Tanner match was like all the quarterfinals, a match of opposing styles, with Lendl holding the baseline against Tanner's attacks. Later, Lendl said he wanted to wait Tanner out "like on clay," even though he knew the surface was much faster. "Beating Tanner on fast Supreme! Pretty good!" he said.

Indeed. In the first set, Lendl broke Tanner's serve twice, in the third and ninth games. Asked if that was unusual Tanner said, "Not when I lose." a

Tanner's 153 mph serve was erratic. He served six aces in the first set but also missed many first serves. "He didn't get many first serves in, Lendl said. "Then they went in they were good. I was just happy to get them back."

Tanner got back a break, in the eighth game to even the set at 4-4. "I break in first set and lost the break," Lendl said "That's no way to play like this. I miss three forehands and one backhand. If I miss two, fine, but four in a row . . ."

Tanner squandered the opportunity by losing the next game. "If I held at 4-4 . . ." he said. "I had the breaks to get back in it, but I just wasn't executing well."

Tanner said he wasn't "doing too good in anything. Maybe it was his play. My approach shots were coming in at three miles an hours, not too hard to pass. I didn't hit the ball hard or cleanly.

"The vollyes were shoulder high or in the net. But a lot of that was his shots. He hits with topspin and whips it around quite a bit."

Tanner continued to play erratically in the second set. Lendl, broke his serve in the fifth game. Down just one break, Tanner had his best chance to even the match with Lendl serving, leading 4-3. But Lendl sealed his fate with an ace that ended the game, and ultimately the match.

Lendl and Tanner were paired in doubles last week in Memphis. Tanner said. "I knew what he could do. I knew he was good. His biggest problem is that he doesn't realize how good he is. Maybe he will now."

If Lendl was the day's giant killer, 6-foot-7 Victor Amaya was its Goliath. Amaya, a big man with a big serve, slew second-seeded Harold Solomon, the man with the slingshot ground strokes.

Amaya, seeded sixth, served 13 aces. Solomon, who has not played in this tournament since he won it in 1975, said, "When Victor is serving that well, I can't afford to play loose points, and I made lots of backhand errors."

Solomon won the first set. But in the second and third sets, when Amaya broke Solomon's serve three times, Amaya said "about 80 percent of my first serves were going in."

Amaya, 25, said "there really wasn't any turning point. I broke him the first game he served in the second set and held on the rest of the way. In the third set, I hit a couple of really good forehands to break at 1-1 and held on."

The two have played only twice: last night, and last week in Memphis, where Solomon won.

"Both matches were really close," Amaya said. "It was a couple of points at the right time. No one style is better. Last week, I played Harold and his style won."

In a parallel, though perhaps even closer quarterfinal match, third-seeded Eddie Dibbs defeated John Sadri, 7-6, 4-6, 6-3. This time it was Dibbs, the ground stroker, who prevailed over Sadri, the man with the gargantuan serve. Sadri, had 24 aces up his sleeve.

Except for the players and the outcome, the matches were virtually identical. With Dibbs serving and staying at the baseline, as Solomon had earlier, the points were long, the players trading ground strokes. With Sadri or Amaya serving and coming to the net, the points cleanly demonstrated the art of serve and volley.

In the first set, Dibbs and Sadri played to a standstill there were no breaks, and Dibbs finally won the set on a tie breaker (despite two aces from Sadri). In the second set, Sadri broke Dibbs on his serve, hitting three consecutive aces. Sadri won the set, 6-4.

But then Sadri tired. After breaking Dibbs in the third game of the third and final set, Sadri double faulted twice and failed to get his first serve in twice. Dibbs broke back to even the set at 2-2.

"He didn't get in as many first serves as he did in the beginning," Dibbs said. "But nobody can keep serving like that. I just hoped he would miss a couple of first serves, because I was always in the points.If I got back the serve, I was in good shape."

Dibbs broke Sadri again to go up 5-3, then served for the match and won, 6-3.

Eliot Teltscher, although flu-ridden, defeated Brian Teacher, 4-6, 7-6, 6-2.

"He got defensive on his volleys," Teltscher said. "But I hit some good shots."

Teltscher, 20, from Sebring, Fla., will meet Amaya Saturday. "Right now," he said. "I'm going home to bed. I've been taking cough medicine and antibiotics but nothing seems to help."

Nothing helped Teacher yesterday, either. He started off well, breaking Teltscher's serve in the second game of the first set, the only break of the set.

Teacher, who did not finish playing his doubles match until midnight Thursday, began to tire late in the second set. His volleys began to wander, and some first serves proved elusive.