Coaching in the NBA is a funny thing. One day, you're considered a genius and at the top of your class. The next day, people are calling for your head and questioning how you got your job as head coach to begin with.

We make so much out of teams' head coaches that sometimes we forget that the coaches aren't actually playing the game; they are merely there to guide their players. So, is coaching overrated? The answer is yes, to a certain extent.

Let's take a look at two teams that are considered by many to have the two best coaches in the league: the San Antonio Spurs and the Boston Celtics.

Gregg Popovich

The Spurs are led by Gregg Popovich, lauded by a sizeable portion of the NBA community as the greatest coach in the history of the game. He has won five titles, has made the playoffs every year as head coach and has never won less than 50 games in a non-lockout-shortened season.

This year, however, San Antonio is struggling, entering Sunday with a record of 20-17 and currently on the outside looking in of the Western Conference playoff picture.

The Spurs missing the postseason? What is this sorcery?

Well, when you take into account what happened to them during the offseason, it's understandable. They traded Kawhi Leonard, Tony Parker left for the Charlotte Hornets, Manu Ginobili retired and Dejounte Murray tore his ACL.

Now, obviously, when teams lose key players, the results are going to be bad. This is not rocket science. However, it certainly goes against the logic that the Spurs have this foolproof “system” in which they can plug in any player any succeed.

That is seriously what many people have said over the last decade or so. That Popovich is such a good coach that he can just pull a bunch of guys off the street, throw them out on to the court, win 50+ games and make noise in the playoffs.

But come on; that is just not true.

Gregg Popovich

We tend to forget that Popovich's entire NBA career coincided with the career of a big man who is arguably a top five player in the history of the league. That man is Tim Duncan.

We can sit here and pine over Pop's coaching excellence all we want, but it certainly helps to have the greatest power forward of all-time and quite possibly the best player of the post-Jordan era for two decades.

The Spurs won five championships with Duncan, most recently in 2014. In addition, Popovich had future Hall-of-Famers like David Robinson, Ginobili and Parker.

So, should we attribute San Antonio's success over the last 20 years primarily to Popovich? Or do we think more logically about the situation and give Duncan the lion's share of the credit?

I will say that Popovich's eye for talent and his ability to keep his team together is unparalleled. That is true. He is phenomenal at identifying players who are undervalued, and his drafting history in conjunction with general manager R.C. Buford is incredible.

If you want to heap praise on Popovich for something, it really should be that rather than his coaching prowess. After all, in spite of having an absolutely loaded roster in 2016, he lost to the much-maligned Billy Donovan in six games in the second round of the playoffs.

Gregg Popovich

If coaching were really that paramount, shouldn't Pop's Spurs have annihilated Donovan's Thunder?

Look; Popovich is certainly a great coach. No one here is denying that. However, sometimes, we give him a little too much credit for his team's success, and he himself has even said this in the past.

Now let's look at the Celtics.

Boston came into this season with the most talent-laden roster in the Eastern Conference and the deepest bench in the NBA, and while the C's certainly haven't been bad, they have not been playing up to par.

In the past, we have heard what a terrific coach Brad Stevens is and how he can take any player and make them look good (hello, Jordan Crawford). That being said, if coaching were really that imperative, wouldn't the Celtics be better than their 21-14 record right now?

This isn't even a knock on Stevens. After all, he is having to re-incorporate Kyrie Irving into a team that made it to Game 7 of the Eastern Conference Finals without him last season, and he is having to integrate Gordon Hayward—who suffered a gruesome broken leg after mere minutes of his season debut last year—into an incredibly deep lineup.

That's two All-Stars and two 20+ point-per-game scorers that Stevens has to mold into the rotation, and that's not even taking into consideration the fact that the Celtics have had to deal with a good sum of injuries thus far.

But I thought Stevens was flawless and that everything he touches works?

Brad Stevens, Celtics

Well, maybe that's not the case. Perhaps there is truly only so much Stevens and NBA coaches everywhere can actually do and that it's up to the 15 players on the roster to go out and perform.

That's why the Celtics held a players-only meeting after a recent loss to the Phoenix Suns, as they knew that the loss had everything to do with them and little to nothing to do with Stevens.

The funniest part about the whole situation is that Boston fans themselves even began turning on Stevens earlier in the year when the C's were 10-10. Lately, the Celtics have picked it up, going 11-4 over their last 15 games, so the Stevens criticisms have cooled down.

It just goes to show that a coach is really only as good as the players he has out on the floor.

Sure; Popovich is a master at working with the Spurs front office to bring in new talent, and Stevens may be a genius at drawing up plays out of timeouts, but in reality, there is limit to how much even well-renowned basketball minds like those guys can do.

Is this to say that coaching is useless? No, but we certainly make too much of it at times and don't give enough credit—or enough blame—to the players actually playing the game.

Or do we think that Tyronn Lue was a big reason why the Cleveland Cavaliers won the title in 2016?