E.B. White wrote that he knew spring had arrived when he walked out the door and "noticed that the air that had come in was not like an invader but like a friend who had stopped by for a visit."

Mr. White is not a New York Mets fan.

For if he were, he would know that the season had officially changed when the slightly southern, slightly nasal and slightly canine voice of Lindsey Nelson returned to WOR-TV.

Lindsey Nelson was the New York Mets. In the lean years of 1962-1968, he spoke like an indulgent uncle, viewing the unreasonable incompetence of this "baseball team" with the serene knowledge that somehow this all could change. Like the good company man he always was, he touted the virtues of the Larry Stahls as well as the Tom Seavers, the Don Boschs as well as the Cleon Joneses.

And when the Miracle of 1969 arrived, and the New York Mets won the World Series, he, like the team and like the city, viewed it with the same combination of astonishment, wonder, and joy. And in the post semi-miracle-of-1973 malaise, he oozed the frustration, if not the anger, of every Met fan.

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"It's shocking to me, too," Nelson said last week from Phoenix. "I was aware that it couldn't go on forever and I was as happy with the Mets as I could be. At this stage, I just wanted to make a personal adjustment."

Nelson, a widower for six years, said he took the job as broadcaster for the San Francisco Giants so he could be close to his daughter, a graduate student at the University of Southern California, who plans to settle in California.

"I cared a great deal how I left New York. I was so happy with the reaction to my leaving. Around town, people universally wished me good luck. Baseball is the only sport in which this happens 'cause you're with the people every day and twice on Sunday. It's a very personal thing."

To understand what the departure of a Tom Seaver from New York or a Luis Tiant from Boston really means, one must understand the game as Nelson does. Baseball is a regular part of people's lives--not a once-a-week cathartic orgy of violence like football, or a repititious, unemotional sprint like basketball. Baseball strolls into America every spring, a welcome member of the family returned home for an annual visit.

Nelson has the same familial bonds that many baseball fans feel toward their teams. "I'll always be a Mets fan. I don't have to tell you what the most exciting day of sports broadcasting was for me. In that fifth game of the World Series in '69, I thought of what I had gone through with that team. Just before the end of the game, it dawned on me--the New York Mets were going to win the World Series."

On that October afternoon Nelson was far from alone in that single wonderful second when he realized that this "bunch of young kids that love to play baseball," as Tom Seaver described them, were goin' to do it.

"That night we drove into Manhattan. I can assure you I never saw such joy in a big city. I can look back at one day when there was joy and happiness. I don't think you coulda got mugged in the subway that day," Nelson said.

He savors that wonderful, old feeling and talks about it with the same earnest enthusiasm he would invoke after a two-out single in the bottom of the ninth of a meaningless August game with the Phillies. Nelson made his love for the Mets as distinct as the not-found-in-nature color of one of his unlimited collection of hideous sport jackets.

And Mets fans loved him. Despite his endless, needless journeys up and down the range of audible sound, despite his awkward promos for Ball Day and Banner Day, and despite the resolute sameness to every Nelson broadcast, he was always the Mets, that most flawed of baseball teams.

Like the banished Jim Woods in Boston, Nelson came with the team, like the stick of gum with a pack of baseball cards--the game of baseball changes and, as inconceivable as a Met season without him sounds, opening day is April 2. It's opening day number 18 for the Mets, the first ever without Lindsey Nelson.