Orlando, Fla. ? Doc Rivers is suddenly a great coach.

An all-star coach.

Potentially even a championship coach.

How does this happen? How does a guy who was fired in Orlando after a mediocre five-year run become the hottest coach in the league? How does a guy who was on the verge of being fired after compiling a 102-144 record during his first three years in Boston become the coach of the Eastern Conference all-star team?

In one year, how does Doc transform himself from idiot to genius?

Did he take a crash course on low-post offense in the offseason?

Did he go to a career-altering seminar on the ins and outs of the pick-and-roll?

Did he go to L.A. and spend the summer soaking up John Wooden’s knowledge?

What’s up, Doc? Why are you a better coach now?

“Better players,” Rivers said openly and honestly before Hedo Turkoglu hit a buzzer-beating three-pointer to lift the Magic over Doc’s league-leading Celtics 96-93 Sunday. “It’s no secret. This is a league of missing and making shots. When you have the right players, you’re a better coach.

“Each year you get better, and I’ve learned a lot since my first year as a coach in Orlando. Having said that, if I would have had these same players in Orlando, we would have had a good record, too.”

This brings up an interesting point: just how valuable is an NBA coach?

Doc is the perfect illustration of how there’s really no appreciable difference between a bad NBA coach and a good one. In Orlando, he was a bad coach because he was saddled with a bad roster. In Boston, he is a good coach and his team has the best record in the league. Why? Because the Celtics added two potential Hall-of-Famers – Kevin Garnett and Ray Allen – during the offseason.

Here’s the ultimate philosophical question when the topic of “great” NBA coaches is brought up: If they can only win with great players, then are they truly great themselves?

Isn’t it possible that you could take a really good high school coach, pay him $100,000 a year, give him the Celtics’ talent and watch him win a championship?

“Yeah, I think I could win with the Celtics roster,” says Travis Jones, the successful coach at Winter Springs High. “Absolutely.”

Let’s look at three guys who are commonly believed to be among the NBA’s greatest coaches of the past 20 years-Pat Riley, Phil Jackson and Larry Brown.

Jackson, of course, won six titles with Michael Jordan, Scottie Pippen and the Bulls. He won three more with Shaq and Kobe. But since Shaq left the Lakers, Jackson has yet to win a playoff series. Are you really “great” if you can win only with at least two Hall-of-Famers on your roster?

Brown? His last year with the Knicks he was 23-59. If you’re really “great,” don’t you find a way to keep from losing more than twice as many games as you win?

Riley won multiple championships with Magic, Kareem and the “Showtime” Lakers. He won another title with Shaq, Dwyane Wade and the Heat. But now that Shaq is old and the team is bad, where is Riley’s genius now? The Heat are 9-33, coming off a 15-game losing streak and clearly the worst team in the league.

If Riley and these other guys are great coaches when they’re winning championships, does that make them horrible now?

Or, probably more accurately, are they neither that good nor that bad?

Aren’t they all pretty much the same – just decent, hard-working coaches waiting around for great players to take them along for the ride?