Cooling thought for openers: Capitals' home NHL season begins Oct. 14 vs. Pittsburgh Penguins; the hockey big league cools it until Oct. 12 this year, 2 weeks later launching than usual. Meantime, the New York Mets have signed a letter of intent to play basketball in New Jersey and the het-up Knicks are belching smoke.

The Nets' lease on Nassau County Coliseum at Uniondale, N.Y., on Long Island expires this ummer and negotiations for renewal "broke down," conveniently for the NBA tenant yesterday. Owner Roy Boe coupled the announcement to that effect with his grand design to move the club to the Rutgers University arena in New Brunswick that will be ready by fall (8,500 permanent seats, room for 3,000 temporary in addition) until a new arena proposed for the Hackensack Meadowlands, adjacent to Giants Stadium, can be built by the New Jersey Sports Authority.

Sonny Werblin, the Rutgers man who heads up the authority is motivating force in the plan to add pro basketball to the package of goodies in the Meadowlands; the states has started a study on feasibility of a 20,000-seat arena, and it might become a reality within two-three years.

The Nets rank 21st of 22 NBA teams in attendance last season (6,935 a game) and Boe said, "It is unfortunate that basketball has not, and apparently will not, attract fan support in Nassau Coliseum." (Did he expect otherwise after peddling away Dr. [WORD ILLEGIBLE]

But there are the Knicks, so incensed that Boe went to federal court for a temporary order preventing them from suing in any other court to block the Nets' move. The Knicks argue that when the Nets came into the NBA a year ago, their indemnification agreement included certain specific territory restrictions. Mike Burke, Knick president, insists: "One of the areas from which they were excluded is the state of New Jersey. This is very valuable territory for us. The Meadowlands is only a few hundred yards [actually, some miles] away from Madison Square Gardens. Many of our fans come from New Jersey. It's our home turf, our territory, and we have no intention of giving it up" . . .

And the site of the Nov. 5 Ken Norton-Jimmy Young heavyweight fight? Promoter Don King says Las Vegas has inside track but Capital Centre has a shot: "After all, Landover is my home, I have a very good friend in Abe Pollin" . . . If Jerry Quarry has a friend, maybe he can be talked out of whatever he's thinking of with the application he took out in California yesterday for a license to fight again. He quit two years ago after Norton stopped him in five . . .

If turnabout is fair play, what could be fairer than Ben Booker?

There was a Ben Booker benefit tournament early this season in fast-pitch softball, a sport in which Booker is a 1977 nominee for the area hall of fame. Now Booker, whose heart - after four coronary attacks - is still in softball, announces a tripleheader to benefit the Hyattsville family of David McDevitt, the softballer out of Gallaudet fatally struck by lightning recently in Cincinnati.

It's scheduled Friday at Rip's Memorial Field, Rts. 301 and 197 in Bowie; a girls all-star slow-pitch doubleheader starting at 7 p.m., then at 9:30, men's fast-pitch, the Ben Booker Prince George's County All-Stars vs. the Jumbo Tures All-Stars of Annapolis. Admission - a drop in the contribution bucket at the field.

There'll be celebrities there - Redskins, Capitals, Bullets, politicos, softball hall of famers," promises Booker of this follow-up once the WWDC-Hyattsville A. C. benefit in Riverdale that raised considerable for the McDevitts.Not the least of the notables - although he has dwindled from 252 pounds to a mere 200 - would be Booker, if he's up to it.

Booker, 53, of Hillerest Heights, fast-pitched 1,044 wins in 1,145 decisions over a 37-year span when not otherwise occupied writing sports for the Enquirer Gazette of Upper Marlboro. "I was nominated for the hall of fame by Bill Collins - an umpire I used to argue with. Oh yeah, he did one of my seven perfect games (among 46 no-hitters)."

Now Booker faces treadmill and catheterization tests in September that will determine whether open-heart surgery is in store. So how much did the Ben Booker benefit tournament raise toward his costs? "Not all that much - anyway, I plowed it back into the softball league." . . .