When a star falls in the NFL, another is supposed to rise in a hurry. Whether he's ready or not. So while everybody in RFK Stadium was saying goodbye to Joe Theismann for the season early in the second quarter last night, Jay Schroeder was trying to prepare in a few minutes for a chance not supposed to come for a few years.

The crowd sensed Theismann's injury was serious long before the stretcher arrived. He had gone down several hundred times before in 12 seasons as a Redskins quarterback, but never quite so frighteningly. What happened was his right leg bent at an ugly angle and 477 pounds of Giants (Lawrence Taylor and Gary Reasons) were piled atop it.

Partly because of how bad the break was and partly because he has been a tough and worthy opponent over the years, several Giants walked by the stretcher and wished Theismann well. So did many Redskins, including Jeff Bostic, whose mind must have been flickering in reverse-frame, to his, similar, departure more than a year ago in St. Louis.

These were good gestures -- and well-deserved. But sentiment lasts only so long. And on the sideline, the tall blond -- whose most recent throws of any consequence had been as a minor-league catcher -- was getting warm. Coach Joe Gibbs had trusted Schroeder for just eight official passes since drafting him out of UCLA in the third round in 1984.

Guess what?

The kid was sensational.

Extraordinary.

Extraterrestial maybe.

So it wasn't quite like Olivier suddenly sidelined with the sniffles and an unknown who happens to be Charlton Heston leaping to the stage and making everyone in the theater forget anyone else ever did decent Shakespeare.

But has any quarterback under similar conditions ever had a more remarkable debut? Not Johnny Unitas. Not Sonny Jurgensen. Not even Sammy Baugh, who did lead the Redskins to the NFL title his rookie year.

Voices from Dallas might argue for Clint Longley. But all he did was throw one memorable -- and lucky -- pass. Schroeder completed 65 percent of his passes against the statistically best defense in the entire league; even the most stone-hearted bottom-liner would have been satisfied with those numbers in a dignified loss.

Dream on.

Midway through the final quarter, the rookie with almost no quality practice time executed a play that even veteran Theismann has been troubled with much of this season.

Needing to hit Clint Didier on the run with a high-outside pitch a few inches from a flailing Giants defender, Schroeder did exactly that. With such inspiration, Washington hardly could lose -- and didn't.

Keep your mind humming long enough to consider:

Could anything be much more sad than Theismann's departure?

Could anything be much more stunning than Schroeder's relief effort?

Before the thrills began, many familiar with the Redskins scarcely could believe they were favored. Those linesmakers ought to be dispatched to Geneva, or anywhere genius is required.

With a patchwork offensive line, with a rookie at strong safety and with a quarterback with just four completions under his belt, the Redskins won -- and by the precise point-spread.

Like Schroeder, some Redskins not expected to be very good were; a few Redskins expected to shoulder some of the extra burden did not. Matters were so bizarre that John Riggins and George Rogers were benched for fumbling; a notorious fumbler, Keith Griffin, was given custody of the ball with pressure at its most intense.

It all got so unreal that you considered the possibility that Schroeder had drifted in from points unknown carrying a football he'd stitched with the legend "Wonder Boy."

"I asked Jay at halftime: 'Want me to cut down on the game plan?' " Coach Joe Gibbs said. "He said: 'No, we'll do it all.' "

That they did. The first pass Schroeder threw in the game went for 44 yards, to Art Monk: the first play of the second half went for 50 yards, again to Monk.

That 50-yarder followed another special bit of daring-do: an onside kick. This was the first of two such successful onside squibblers.

Which means that Steve Cox rates some sort of quadruple-threat mention, having punted, thrown a pass off a fake punt and completed it, kicked off and recovered an onside kick.

Schroeder's was the rapidly-ascending star. In addition to the obvious, he also did well as the substitute holder, even though Mark Moseley missed an extra point that caused the tension to be even tighter.

Some background:

Schroeder has gotten almost no practice time since training camp that would have helped him last night. Mostly, he is an impersonator, playing the role of opposing quarterback to give the Redskins defense the best idea of what to expect each week.

He has been Danny White twice this season, Ron Jaworski, Bernie Kosar and, this week, Phil Simms. As himself, Schroeder was even better. Cool and accurate under pressure. Or exactly what Theismann had not been of late.

There was a hint of Schroeder's calm in chaos when he was forced to punt during the Bears game and did well. Ironically, he also replaced Theismann in that role.

One of the reasons Theismann had not been vilified for playing poorly is that few thought Schroeder an adequate alternative. To bench Theismann in favor of Schroeder before the Redskins were eliminated from the playoffs, many thought, would be unfair to both.

Guess he's ready right now. He has to be.