AGENT BELIEVES MAGIC WON'T CHANGE HIS MIND.

Exactly three months shy of his 37th birthday, Magic Johnson is no Comeback Kid.

Which is to say that after announcing his retirement Tuesday for the third time in a 13-year playing career, Johnson probably doesn't have enough time to make another NBA comeback even if - or is that when? - he gets the urge.

``He's not changing his mind,'' Lon Rosen, Johnson's agent, said Tuesday afternoon. ``He's retired.''

Rosen knows better than anyone else that the fickle Johnson, who contemplated numerous comebacks before rejoining the Lakers on Jan. 29, is ``going to want to play until he's 80.''

But Rosen also knows that ``there's not many more years he can talk about.'' Especially since Johnson, still well over his prime playing weight despite losing 15-20 pounds during the comeback, played with calf and heel pain for much of his 36-game stint counting the playoffs.

``He definitely could have played next year,'' Rosen said.

From a fitness standpoint, yes. But if Johnson was somehow convinced to make one last comeback - by, say, a certain Mr. Riley in Miami - he'd face another obstacle.

Once Johnson formally notifies the NBA of his retirement by sending in a letter, it would take a three-fourths vote of the league's Board of Governors to re-instate him for the 1996-97 season.

``Earvin's happy,'' Rosen said. ``He's really happy. I think you'll see that (today at Johnson's news conference).''