With Don Nelson, the contradictions are staggering. There’s 31 seasons worth of them, all etched in stone.

And on a Wednesday in April of 2010, Nelson wrapped them all up and laid them on the doorstep of the National Basketball Association like some sort of petrified dinosaur’s egg.

He’s the NBA’s all-time winningest coach.

And he’s won nothing at all.

Come again? How does this happen? How do you stay employed for 3,000 basketball games (including exhibitions and playoffs) and never come close to winning it all?

He’s a monument to mediocrity. Or to bold experimentation, depending on how much you’ve bought of what he’s selling.

For whatever reason over the years, people have bought a lot of what Nellie had to offer, which was the gimmickry of small ball, the lightning strike of scoring and quickness.

He coaches teams that can lead the league in both points and frustration.

Okay, okay, on many, many nights it was a hell of a lot of mad fun. As Phil Jackson liked to say, nobody could muck up a game like Nellie.

But it has gone almost nowhere. In the 1980s, Nelson’s Milwaukee Bucks teams won six straight division titles, but they whiffed each year in the playoffs. Despite having coached more pro basketball games than any other human being not named Lenny Wilkens, Nelson has a playoff record of 75-91, a winning percentage of just .452.

As triangle offense guru Tex Winter observed two years ago, Nellie’s teams could give you fits on any given night. But he pursued an agenda that simply couldn’t hold up over a seven-game playoff series, not against the league’s top teams.

“He’s always been able to make other teams play the way he wants to play instead of the way they want to play,” Winter said. “He sees the game and he has ideas about how it should be played.”

During the regular season “small ball” always presents opponents trouble as a “one-game philosophy,” Winter pointed out. “But it becomes a question mark when you get locked into a seven-game playoff series. That changes things considerably for those teams that want to play small ball or run a lot.”

Nelson rang up a couple of 60-win seasons, and a 59-win season, plus innumerable other good campaigns. None of them amounted to anything more than steps on that NBA treadmill known as the regular schedule.

Which suggests a life misspent. Why the hell didn’t he coach college basketball? With the one-game playoff format in the colleges, he might have mucked his way to an NCAA title or even two in 31 seasons.

Instead, he’s mostly a testament to the NBA’s own weird parlor game of franchise monopoly. At the very least, you can say that no one has ever done a better job of beguiling team owners and selling them on the big dream just around the corner, the big payoff just a little further down the road.

In that regard, Nelson has managed to make mediocrity profound. And he’s done it in a big way over parts of four decades.

That’s worth something, right?

He’s won 1,333 regular-season games (against a thousand and sixty some losses), and he’ll close out this season with perhaps a few more than the previous all-time winningest guy, Lenny Wilkens.

Okay, that’s at least worth a nod of respect. If nothing else, Nelson is a freakin’ locomotive, a lifer with a three-thousand-game stare.

But Lenny’s got it all over Nelson because Lenny owns something that matters. He owns a ring, earned by the sweet virtue of coaching the Seattle SuperSonics to the 1979 championship.

If Nelson wants to think about championships, he’ll have to close his eyes and go back to his days as a role player with the Boston Celtics

He played on five championship teams (1966, 1968, 1969, 1974, 1976), and he owns that most special of moments late in Game 7 of the 1969 championship, when Boston was leading the Los Angeles Lakers 103-102 and Nelson picked up a loose ball and pitched up a wounded duck of a shot that struck the back of the rim, rose up and fell through, thus sealing the deal on Jerry West’s personal hell.

Yes, whenever Nelson wants to smile a championship smile, he can think of that one and chuckle.

As for Nelson, the coach? Well, he’s been able to hang in there. You  don’t coach that long without being a hell of a competitor, one who has endured through thousands of nights, often with fewer resources, one  who has battled cancer and heartbreak and managed to keep on fighting. That means he owns a piece of the competitive emblem of the NBA. You can never take that away from him. Some people want to compare him to Jerry Sloan. Nellie’s no Jerry Sloan. Sloan has long known what it takes to win in the NBA and has pursued it relentlessly.

Nellie has amused us, and himself, on a lot of otherwise dreary nights in Milwuakee and Dallas and San Francisco. They even allowed him a short stint on Broadway.

For this, he’s cashed very big checks, traveled the world on private jets, summered in Maui, driven expensive cars, supped at the best restaurants, slept in the best hotels — and gotten the vacation started early every season.

It’s been a good time. A good, long time. And that will have to be enough for Coach Nellie, who these days is getting used to the notion of being 70.

He wanted to prove a point about small ball being the way to win it all, and we can safely say 3,000 games later that he never made that case, not even close.

Roland Lazenby is the author of Jerry West, The Life And Legend Of A Basketball Icon, recently released by ESPN Books.