Roscoe Tanner, who hammered Bjorn Borg out of the U.S. Pro Indoor tennis championships with an electrifying performance Friday night, was not as sharp yesterday afternoon, but still served 23 aces in beating sluggish Eddie Dibbs, 7-6, 5-7, 6-4, 6-1, in the semifinals of this prestigious $225,000 Grand Prix tournament.

The 26-year-old lefhander from Palm Springs, via Lookout Mountain, Tenn., will play one of his contemporaries - topseeded Jimmy Connors or third-seeded Brian Gottfried - for the $35,000 first prize on Sunday. Connors and Gottfried were paired in a late semifinal last night.

Tanner served aces on the first and last points of the tie breaker that won him the first set (7 points to 2). He lost the second set on a double fault. He grasped the third on another ace, his 18th. And he served back-to-back aces in the games that gave him 3-1 and 5-1 leads in the fourth set, contributing to Dibbs' obvious and growing discouragement.

Aces are flashy moments in a tennis match - much as tape-measure home runs are in a baseball game, regardless of the score - and counting them gave the crowd in the cavernous and less than half-filled Spectrum a diversion. But the match itself was really rather dreary, totally lacking the spark and emotion a near sellout crowd of 15,000 gave to Tanner's 6-4, 7-6 conquest of Borg 15 hours earlier.

Obviously, the serve is Tanner's most potent and spectactular weapon - a conversation piece for spectators and the linemen behind the court who live in fear of being maimed by his missiles. One was struck yesterday, but lived to call the next fault, and was amused when Dibbs asked if he'd like to take cover.

But it was not the winning serves that gave Tanner the upper hand, although he is the first to admit, "If the first two points of a game are aces, I'm going to go for a third and a fourth, I enjoy that. Sometimes I can pull myself up with my serve if I'm demoralized, or stop a landslide by hitting a cluster of aces."

More important was the consistency of his serving - except for a brief patch in the middle of the match when he started rushing - and the way he backed it up with his volleying and ground games. Tanner's ground strokes have improved enormously through intensive work with former U.S. Davis Cup captain Dennis Ralston the past 2 1/2 months.

"I felt my ground strokes were going well enough that I could go for more on my first serves and not worry if I missed some," said Tanner, who came to the net behind every first serve on the medium fast synthetic surface but followed his second delivery in "just enough to keep Eddie guessing."

Against players like Borg and Dibbs, who return exceptionally well off both wings and like to stay in the backcourt, Tanner believes that the most important thing is to mix his serve up smartly, like a pitcher challenging a good bitter - changing pace, nibbling at the corners, leaning back for the high hard one only when really needed.

"I don' judge my serve by aces, but by whether I'm holding it or not. That's the measure," he said. "Most of the aces I served against Eddie were not hard, flat ones. They were spin serves - slices out wide in the ad court and dwon the middle in the deuce court."

Actually, Tanner - the No. 10 seed who has beaten llie Nastase. Borg, and Dibbs in succession - would have won much more easily if the hadn't missed an almost embarrassing number of backhand returns.

But when his ground strokes started to go away - "that usually means I'm not moving my feet" - there was always the serve to bail him out.

"When he starts getting the first one in, there's no way to get it back unless you guess right, and even then your return ususlly sets up his volley," shrugged Dibbs, the 5-foot-7 hustler known as "Fast Eddie." He said he felt slow and stiff after his three-set victory over Sandy Mayer Friday, but admitted this probably made little difference.

"Roscoe's whole game revolves around his serve. If he's serving well, the other things fall into place," Dibbs said. "But he's also hitting his ground strokes better, forcing more from the backcourt."


Tanner. Gottfried, Stan SMith and Dick Stockton bagan working last fall with Ralston, the top-ranked player in the U.S. in 1964. 65 and 66, and a keen analyst of the game. Because his home is now in Palm Springs, where Raiston teaches.Tanner has been the player most dedicated to the Davis Cup-style training program, which includes six-hour days of running, exercises, drills and painstakingly disciplined practices.

Ralston is also a tactical adviser except when members of his little flock play against each other. Before the Borg match. Tanner called Ralston and made a little list.

"Concentrate" . . . "Be patient" . . . "He goes cross-court on short balls" . . . "Come in some on his second serve" . . . "On brack point, move the ball around." Those were the notes Tanner jotted on a hotel pad from his long-distance strategy conference. He stuck them in his racket cover and referred to them at change games - and they served him well.

Tanner called Ralston again after the Borg match. he got some pointers for Dibbs, but didn't bother to write them down. %Just little things; I kept them in my head," he saie.

He never felt pressed, even when he let serveral golden gopportunities to take command of the second set get away after coming back from 1-4 to 4-4, 15-40 on Dibbs' serve, with a string of eight consecutive points that included a cluster of three aces.

He let three break points get away in that ninth game - netting an easy, midcourt overhead on one - and two more in 11th game, then saved four set points in the 12th game only to double-fault on the fifth.

Tanner survived two break points in the second game of the third set - Dibbs mis-hit a backhand volley off a fierce point, then flubbed a backhand return - and was over the last hill. He broke Dibbs at 30 with a backhand cross-court volley in the next game, and lost only seven points in seven service games thereafter.

Dibbs, unremarkable throughout, collapsed completely in the final set, losing his serve three times in a row, the last two on double faults. Quite simply. Tanner lived by the serve and Dibbs died by it.

South African Davis Cuppers Bob Hewitt and Frew McMillian beat Stockton and Marty Riessen, 7-6, 7-5, to advance to the doubles final. They will play the winners of Rose Case-Syd Ball vs. Vitas Gerulaitis-Mayer.