Nate Thurmond, whose arrival on the Cleveland Cavalier scene Nov. 27, 1975, was the turning point toward the erswhile NBA doormat's surge to its first playoffs, will not be playing any more this year. Maybe not ever again. He is going on 36, and his "good" knee is wrecked.

The 6-foot-11 defensive stalwart who provided the inspiration that lifted the Cavs into that rousing seven-game series with the Bullets, which he played no small role in winning, tore up his left knee Tuesday night. The NBA's No. 4 all-time rebounder - more than 14,000 in a 14-year career - was hurt trying to save a ball from going out of bounds during the loss to Houston.

"That's it for the year," acknowledged spot-player Thurmond, who twice in his career had surgery on his right knee. "I know from experience it will have to be operated on. I just don't know if, at my age, I can come back (next season) from another operation . . . I did not want to go out being carried off the floor. I have dreamed of ending my career . . . walking off the floor," he lamented after being helped to the locker room by two teammates.

Maybe the Cavs weren't so dumb after all in picking up Elmore Smith last month to help out at center . . .

Day by day the two-year, three-year, five-year (plus option) contract signings trickle in from the baseball front, pointing to a considerable measure of stability after the great 1977 money war. The American League West champion Kansas City Royals have not announced a signing, but general manager Joe Burke says don't worry about 'em, "We've been signing players since December." Burke, former Senator official, reminds, "This is a crucial year - the start of the six-year reserve clause (under the agreement that allows a player with five years in the majors to become a free agent after his sixth season. So if we don't sign players in those classifications to multiyear contracts, we could lose them. Happily, we're going to sign most of them."

The Royals also happily announced a season-ticket sales record, 6,815 eclipsing the 6,805 of the club's 1969 maiden year - but coupled the announcement with the familiar unhappy refrain around the majors in recent years: Tommy Davis has been released. The 17-year vet had five hits in 19 trips in the homestreth after being picked up from the Angels Sept. 20 . . .While their stars hestitate about signing contracts, the Cincinnati Reds' fan show faith: they've provided the earliest sellout ever for baseball's opener, April 6 vs. San Diego . . . Talk about speed, all 1,300 seats in the Hartford Civic Center were snapped up Monday, first day of ticket sales, for the March 22 performance of Nadia Comaneci and the Romanian women's gymnastics team (at last look, ads were still running for the same show March 15 at Cole Field House) . . .

Look to your laurels, bowlers from the Midwest hotbeds: Bob Ford (278-680) and early bed in regular doubles at the ABC tournament in Reno, Nev. - they're from Alexandria, Va. . . . Fran Brock made a note in a recent ABC national newsletter, breaking 600 for the first time in a big way: 699 in the Guys and Doll s league at Fairlanes Wheaton Plaza . . . And nobody we know of has topped the world record 258 duckpin game James Stansbury of Severn, Md., chalked up this season in Park and Planning Mixed League at Prince George's Plaza . . . Or the 215-212-148 - 575 series by Dick Westlake of Weaton at the Glenmont Bowl . . . An eye-opener from the Women's International Bowling Congress: 1,227 tenpin rollers converted 7-10 splits last year. Believe it or not . . .

And believe this or not: One Paul Corvino, sports promoter, says he and Don King are negotiating to produce a Muhammad Ali heavyweight title defense in Seoul, in early May, under sponsorship of Han Kook, owner of the Korean Times, and with the gung-ho blessing of South Korean President Park. Charlie Lomax, Ali's attorney, confirmed the possibility and vouched that "Herbet Muhammad (Alis guiding hand) is working on the deal with Corvino" . . . Word is that the telecast portion (ABC) of King's tournament bouts at Annapolis on Sunday will focus on the light-heavyweight fight between Biff Cline of Hilcrest Heights and Ray Elson and the Johnny Boudreaux Scott Ledoux heavyweight tiff . . . Comes now the 11-round fight. The bout between light-heavies Mike Rossman and Mike Quarry, originally to be a 10-round prelim to Ken Norton-Duane Bobick in Madison Square Garden March 2, has gained one round and top billing since Bobick's bowout with a rib-area sprain . . .

Ross is the half-Italian who boxes as "The Jewish Bomber," but Chris Cline, Biff's father/manager, serves notice on the ring world to watch out for his "authentic Jewish heavyweight" - Mike Luftman, former Parkdale High football linebacker. As the 190-pounder Luftman, who has three amateur KO's in 50 seconds or less in three bouts, pounded the bag at Hillcrest Heights Boys Club, Cline allowed, "When I look at him I see $$$." So, we can say we knew him when, but, for now, Luftman settles for "champion by default" of his division in the Golden Gloves tournament that runs at Prince George's Community College the next few weekends. There will be some 250 combatants, the best of them to win trips to the national finals in Hawaii . . . The Lions Club co-sponsors the Gloves, and the area Lions also do good the night of Feb. 23 - the Indiana Pacers-Bullets game will be a benefit for their District 22-C sight and hearing conservation program . . .