For decades, Paul Zimmerman was Sports Illustrated’s “Dr. Z,” the analytical and opinionated football guru who penned erudite and insightful columns, picked games, wrote mock drafts, knew everybody and was known by everybody.

But before Zimmerman worked his word magic for SI, he did so for The Post from 1966-1979 — covering the Jets, writing general sports columns with an emphasis on the NFL and becoming an early pioneer of in-depth analysis using the then-new technology of videotape. He even wrote a wine column.

Thursday, when Zimmerman died at age 86, he was remembered by colleagues as a writer who brought unique insights into the game, who never shied away from a strong opinion and who worked hard at the science of his craft.

“After a Jet game at Shea [Stadium] he would come into the office down at 210 South Street and he would watch whatever game was on — and he would sit under the TV and chart the game — two teams from outside of New York,’’ said Steve Serby, now one of The Post’s NFL columnists but then a young football writer.

Zimmerman learned the game from the inside out, having played on the offensive line for Lou Little’s Columbia Lions teams.

He could tell you not just that a running back broke one for 40 yards, but that he did so because some unsung offensive lineman had freed him up with a fundamental, little-noticed move.

“He was very knowledgeable, he just knew football,’’ Serby said. “The offensive line was his thing, and everybody knew who he was.’’

Phil Mushnick, then a clerk in The Post sports department and now a sports media columnist, recalled Zimmerman as a writer for readers and fans, first and foremost.

“He had an opinion,’’ Mushnick said. “He didn’t get along with Joe Namath, and he wrote why.

“He never left you guessing what he was thinking. He wrote for the readers, not for the subject, and he didn’t write to curry favor.’’

Peter King, Zimmerman’s longtime friend and SI colleague, announced Zimmerman’s death on Twitter.

“We have lost a legend,’’ King wrote. “Football writer/raconteur Paul Zimmerman, 86, died this afternoon. There’s only one Dr. Z. He’ll be missed.’’

According to King, Zimmerman had suffered a series of strokes in 2006 that left him unable to speak or write.

Zimmerman and wife Linda had moved to Indiana, where Zimmerman could be in an assisted living facility and be close to family.

A Philadelphia native, Zimmerman began his journalism career at the Columbia Spectator before moving on to the now-defunct New York Journal-American and World-Telegram and Sun, and then The Post.

He also was a prolific football author, writing, among other works, “The Thinking Man’s Guide to Pro Football.”