NFL PLAYOFFS : Aikman Might Be Ready, but Beuerlein Is Set to Start : NFC playoffs: Cowboys are 6-0 with former Raider at quarterback. Kramer is unbeaten since taking over the helm for Lions.

Mystery writer Erle Stanley Gardner might have called it “The Case of the Missing Quarterback.”

When the Dallas Cowboys (12-5) line up today for the last game of the NFL divisional playoffs, their quarterback, Troy Aikman, will be missing.

He is physically ready to play. “I could have started last week,” he keeps saying.

But Cowboy Coach Jimmy Johnson says that he will send Aikman’s backup, Steve Beuerlein, against the NFC Central Division champion Detroit Lions (12-4).

Aikman, a former UCLA quarterback, will be on the sideline again during the game that will provide the Washington Redskins’ opponent in the NFC title game next Sunday at Washington.

Former Raider Beuerlein seems to be a valuable backup, but no one ever considered him the top pick in an NFL draft, as Aikman was in 1989.

Noting that the Cowboys were 6-5 when Aikman was hurt and are 6-0 since then, Johnson says: “We feel we’re on a roll right now. We are winning, and Troy is not 100%. So I think the situation dictates Steve starts.”

Aikman’s condition is very much in dispute.

“The (injured) knee feels good,” he told Dallas reporters this week. “I could have started (in Chicago) if they had wanted me to. They didn’t want me to.”

That seems clear enough. But isn’t Beuerlein in better condition?

Said Aikman: “If anyone saw me in practice, they wouldn’t be able to see any difference in my execution now than before the injury.”

Then why start Beuerlein?

Last week, there came a time when the Cowboys probably weren’t going to win if their quarterback couldn’t throw a deep sideline pass. So Beuerlein threw it. He threw it as if he had invented it. And the Cowboys went on to beat the Chicago Bears, 17-13.

Aikman’s arm strength doubtless matches Beuerlein’s. And Aikman’s deep passing has been improving. On the play on which he was injured at Washington Nov. 24, Aikman threw an excellent long pass that was caught in the instant that the passer went down.

Beuerlein, though, for most of his short career, has exhibited a surer long-ball touch.

Also, Aikman has been sacked as many as 11 times this season--in one game. Beuerlein rarely is sacked.

There is the possibility that Johnson wants Aikman to see how his somewhat more nimble backup gets out of trouble and gets the ball away somehow, throwing it away if necessary.

In each of the last two years, injuries have knocked Aikman off the team. And Johnson doubtless reasons that no matter how talented and courageous any quarterback is--and Aikman was born with a full measure of both talent and bravery--neither quality is enough when you have to carry him off the field.

So it will be Beuerlein today against another backup, Erik Kramer of Detroit, when one of the league’s two hottest teams--both are on six-game winning streaks--comes to the end of the line.

Dallas is in somewhat better physical condition than Detroit, which has lost, among others, its leading defensive player, nose tackle Jerry Ball.

The last time these teams played, Ball was very much in evidence as Detroit won, 34-10, on a day when Aikman was sacked twice and two of his passes were intercepted. One of the interceptions was returned 96 yards for a touchdown. The Lions also blocked a field goal and brought it back for a 55-yard touchdown.

The Cowboys outgained the Lions, 415 yards to 208, and still lost in a rout.

These teams’ running backs were rather silent in that game. Neither NFL yardage leader Emmitt Smith of Dallas nor unanimous all-pro Barry Sanders of Detroit was a force. Sanders gained 55 yards, Smith 66.

Detroit’s No. 1 quarterback, Rodney Peete, was injured on the club’s first possession, and the real story of the game was Kramer.

Coming in cold to take his first nonstrike NFL snap, Kramer led the Lions home with two touchdown passes. And he has been leading them well ever since.

“What Erik has accomplished is unprecedented,” said his quarterback coach, Hall of Famer Raymond Berry.

“I’ve never heard of a backup quarterback who never played a down in the NFL taking a team to a division championship.”

Kramer, asked to evaluate himself, said: “I think I’ve done the job. We’ve won a lot of games.”

In the last week of the regular season, when Detroit scored a 17-14 victory at Buffalo to beat out the Bears for the division championship, Kramer completed five for five on the Lions’ winning drive in overtime.

“(Kramer) always gets better as the game goes on,” Detroit Coach Wayne Fontes said.

“That’s been his M.O. since he got here.”

For Beuerlein today, that sounds ominous.

Kramer, however, has never played Beuerlein.