Even its most devoted players would agree that gin rummy has, at best, limited possibilities as a spectator sport.

But watching two old pros go at the game (and each other) turns out to be recreation of a high order. And despite the opinion I heard recently- that this was an improvisational play that varied with each night's deal of the cards-I believe the deck has been stacked-and stacked adroitly-by a knowing playwright.

D.L. Coburn's "The Gin Game," which had its press opening last night at the Eisenhower Theater, is about two old and physcially wracked people who are bitterly unhappy to find themselves in a cut-rate rest home- and bitter about some other things they'd rather not mention. He reintroduces her to the game of gin. She shows a certainflair for it.

If this sounds trying, try to imagine a steaming Hume Cronyn as the old man, dangling semi-focals on his nose, wagging his cane, sharing sarcasms with an imaginary little man perched on his shoulder, and stomping up and down in a cranky rage whenever he loses-which is invariably.

And picture is white-haired Jessica Tandy across a folding table from him, the image of moral rectitude, calmly organizing her cards (although occasionally forgetting she has put one temporarily aside in her mouth), mechanically picking up her opponent's every discard, and squirming and shuddering whenever he takes the Lord's name in vain-which is at least as often as he loses.

There are no other actors in the cast, and no need for any. Cronyn's sturming and dranging, shaded with meek looks and subtle twitches, is the perfect match for Tandy's good-manered gloom, concealing her own rival tempest of hurt.

This old married couple was put through their original paces by director Mike Nichols a year and a half ago, and they have been playing "The Gin Game" almost continuously ever since-in 12 cities, including ours. But if Cronyn and Tandy have tired of life on the road, they did a splendid job of fooling last night's audience.

It is no mere abstraction to suggest that in other hands, "The Gin Game" might be slow going. E.G. Marshall and Maureen Stapleton (both looking far too young and healthy for a rest home) have been demonstrating just that on Broadway for some months now.

But while Coburn's play is hardly a sure-fire vehicle, it has a coolly calculated rhythm that emerges in the mounting temper of the dialogue:

SHE (upset): oh . . . ! I guess I'm sitting here with gin already.

HE (later, with a slightly irritated chuckle): No more lessons for you . . . I knew you were keeping queens!

SHE amazed): You didn't get any points at all in that game, did you?

HE (angrily): That is dumb! That is just dumb gin! Holding face cards that long.

SHE: I won, didn't I?

Time Lapse)

HE (a few hands later, raging): you know, when you get gin you're supposed to put the discard face down!

SHE: I've never seen a man get so wild over a game of cards. It's not natural. There's something wrong.

HE: You know what's wrong with most people in the world today? They have a mother who's just like you!

Between deals, in uneasy gestures of confidence, the two characters reveal a few of the wrongs that have been done them over two unhappy lifetimes, and their enormous sense of repressed anger that no one seems particularly to care. Whatever its frailties, that's where the strength of Coburn's play lies.

There, and in the singular pleasure of watching two people who don't understand each other being portrayed by two actors who could hardly understand each other better.

THE GIN GAME, by D.L. Coburn. Directed by Mike Nichols,. Setting by David Mitchell; costumes by Bill Walker; lighting by Ronald Wallace. Presented by the Shubert Organization.

With Jessica Tandy and Hume Cronyn.

At the Eishenhower Theater through May 12. CAPTION: Picture 1, Hume Cronyn and Jessica Tandy in "The Gin Game." Picture 2, Hume Cronyn and Jessica Tandy in "The Gin Game"