John Cassavetes, who looks more and more like Al Pacino's father as the years go by, certainly has a way with Author's Messages. In the second hour of the four-hour CBS movie "Flesh and Blood," he announces, "Sooner or later in this life, kid, everyone loses. It's part of the deal -- original sin, or something. Nobody's perfect."

Not all the sins in "Flesh and Blood," from a novel by Pete Hamill, are original, but one of them, the suggestion of incest between a mother and her grown son, is rarely brought up on television. If "Flesh and Blood" has a sensationalistic side, though, it is also at times just plain sensational. It brings to TV a toughness and a sadness that are like alien sensibilities inthe medium of the happy face.

The first half of the filmed drama airs tomorrow at 9 p.m. and the second half Tuesday at 9 p.m. on Channel 9. Merely as a story, this tale of a carousing kid turned heavyweight contender -- albeit one who dangles from apron strings -- remains absorbing for most of its three hours and 30 minutes of actual running time.

It also showcases a powerhouse performance by Tom Berenger as the fighter and a sophisticated, adroit one by Suzanne Pleshette as his mother. The best parts of the film may be in its first hour or so, when it details the heartlessness of the city, through expert location shooting in Chicago, and the roughhouse world the kid lives in.

A barroom brawl in the opening scenes quickly sends him off to the pokey, where he learns to fight -- first as a way of self-defense against a homosexual advance an then to get "easy time." Later he lands in the Golden Gloves but is thrown out of amateur boxing after a spectacular match in which he knocks the referee over the ropes. So turns pro.

The incest business was far more explicit and extended in Hamill's book, leading the usual band of professional alarmists to denounce the CBS film before cameras had even turned. To get very outraged over the finished film you have to do an awful lot of interring. Things are kept on the hint-hint side.

Nevertheless, the final scene in the first half -- probabaly the longest single dramatic scene in the film -- is a provocative and, frankly, erotic build up to a freeze-frame suggestion of what will happen, off-camera, next. mom and son are spending a lonely Christmas Eve together, and instead of carols, the radio is playing "The Nearness of you" and "All the Way."

Pleshette has always had an insinuatingly downtown kind of sexuality on the screen, and it works very well for her here. It also helps the writer, Eric Bercovici, and the director, Jud Taylor, because they can rely on a certain unspoken come-hitherness to convey what they dare not get into in dialogue and action.

Taylor has otherwise gone at this story with a bracing, two-fisted style and he had the inestimable aid of Vilmos Zsigmond as director of cinematography. Zsigmond has shot big budget Hollywood beauties such as "Close Encounters of the Third Kind."

The fight scenes in particular are rousingly well done, and Taylor resorts to slow motion only minimally, so that comparisons to "Rocky" or "Rocky II" are out of order. There are such deft touches as a lightning cut from mom's invitation "dance with me," in part two, to the sudden pow of glove against face in the boxing ring.

Berenger, who costarred in the illfated "Butch and Sundance: The Early Years," and was introduced as the murderer of Diane Keaton in "Looking for Mr. Goodbar," shows strength and drive in this role, at times suggesting a cross between a young Brando and a serious Warren Beatty. It is not a bad combination, and it helps "Flesh and Blood" successfully deliver the old one-two.