The Warriors' screens aren't any more illegal than everyone else's

The Warriors' regular-season dominance couldn't be challenged by any opponent on the court this season, but the doubters still found ways to question their greatness. Fortunately, most of that unwarranted criticism has dissipated by now.

There's one controversial topic, however, that refuses to die: The claim that Golden State's offense is as good as it is because, with the help of absent-minded NBA officials, it uses illegal screens to get open looks.

It's impossible to completely disprove this theory, but a close look at the accusation suggests that it largely lacks any merit. There's really no big conspiracy to help Golden State get an advantage. It's all much simpler than that.

The rule book is complex and allows for interpretation

There's a clear disconnect between how fans define illegal screens, what the rules say and what officials typically call. Here is the official language in the NBA rule book. (Emphasis mine).

A player who sets a screen shall not (1) assume a position nearer than a normal step from an opponent, if that opponent is stationary and unaware of the screener's position, or (2) make illegal contact with an opponent when he assumes a position at the side or front of an opponent, or (3) assume a position so near to a moving opponent that he is not given an opportunity to stop and/or change direction before making illegal contact, or (4) move laterally or toward an opponent being screened, after having assumed a legal position. The screener may move in the same direction and path of the opponent being screened.

In (3) above, the speed of the opponent being screened will determine what the screener's stationary position may be. This position will vary and may be one to two normal steps or strides from his opponent.

Many fans believe that a screener must be completely stationary at the point of contact. That is incorrect.

As it turns out, the rule's actual language is quite complex and features several poorly defined concepts instead of offering clear instructions. In practice, that means the officials have to interpret the rules the best way they can. The league actually had to send out a memo clarifying what constitutes legal and illegal screens. Referees are obviously drilled on the subject, but clearly there's a lot more to take into account than whether a screener is moving before blowing the whistle.

Take this play from Game 2 against the Portland Trail Blazers as an example.

Andrew Bogut is moving in the same direction as the opponent, which is legal by the letter of the law. When I first saw that play I immediately thought it was an illegal screen. Bogut made contact with Maurice Harkless and continued to move in a way that obstructed him as he tried to get past him by the left side.

But after reading the rulebook again, I can absolutely see how an official might not call it.

In practice, everyone gets away with setting "illegal" screens

Watching the games closely, it's obvious that the Warriors do get away with some illegal or at least borderline illegal screens. But so do other teams.

Because a lot of screeners toe the line between legal and illegal, officials typically only blow the whistle in blatant examples or when the defensive player sells the contact. If there is a screen that is technically illegal but doesn't really take the defender out of the play, they often let that go unpunished to avoid interrupting the natural flow of the game. Even when those screens do affect how the defender performs, sometimes officials just miss violations.

For example, most screeners let their teammates get by before sticking out their butt or hips, or using their arms to slow down opponents. It's illegal to actually make contact with the defender, but most take the extra step to get around it and stay with their man. Sometimes it gets called and sometimes it doesn't. You can easily find examples of the Trail Blazers -- the Warriors' second-round opponent -- getting away with it often in every game of the teams' five-game series.

The officials sometimes miss obvious calls, but mostly they just use their judgment, both to determine whether there was illegal contact in the first place and whether that contact was significant enough to warrant a whistle.

That's why there are so few illegal screens called per game -- fewer than one per team, in fact -- and why every team gets away with setting some picks that are technically illegal. It's not a strict interpretation of the rules, but as long as no one gets preferential treatment, it's fair enough in practice.

The Warriors don't actually get preferential treatment

We've established that it's sometimes hard to determine when a screen is legal, which is why officials let everyone get away with some illegal ones in every game. The question is whether Golden State gets away with illegal screens more often than others.

From our research, it doesn't seem like they do. There are reasons why many think they do, but there are simple explanations for that.

The Warriors' offensive style and proficiency creates a misperception about their screening. The Warriors led the league in percentage of possessions that ended with a shot coming off screens in both the regular season and in the playoffs, according to Synergy Sports. They also rank third in screen assists in the playoffs, per SportVU. That new measure attempts to credit players that directly create open shots for teammates with screens.

The complaint from their opponents is that they are so prolific and efficient in those area not because their shooters are great, but because they set illegal screens to free them that don't get called. In other words: Klay Thompson and Stephen Curry make shots because illegal screens get them open, not because they are two of the best shooters of all time.

Even despite that, the Warriors comfortably lead all playoff teams in illegal screens called off the ball, with seven in their first 11 playoff games.

Up until the conference finals, Golden State averaged 0.9 total illegal screens calls against them per game in the postseason, the third-most out of any playoff team. Only the Trail Blazers and the Heat averaged more, and it wasn't by a huge margin.

There is a clear symmetry between screen usage and illegal screen calls in general. The teams that screen the most get called for illegal screens the most, and the Warriors screen a lot. Teams like the Cavaliers, Spurs and Thunder that rely more on post-ups and isolations set fewer screens. Therefore, they get fewer illegal screen calls, but also fewer opportunities for people to see the effect of a screen. The reason people misperceive the Warriors' screening legality is simple: They screen and score more often than any other team.

There's also symmetry between the type of screen teams use most often and the kind of illegal screen called. Golden State's offense relies heavily on off-ball screens and pindowns. Therefore, officials both call and miss more illegal screens of that nature. By contrast, officials tend to call and miss more on-ball illegal screens for pick-and-roll-heavy teams like the Heat and Raptors. The Trail Blazers, who use both types of screens heavily in their offense, actually had as many calls against them on the ball than off.

There's nothing really suspicious about the number or the type of illegal screens Golden State has been called for thus far compared to other teams. They just set more off-ball screens in general, so the legal and illegal ones stick in our memory for longer.

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The Warriors do get away with setting illegal screens at times. Their screeners really are great at toeing the line between what's allowed and what isn't. Anyone actively seeking out incriminating examples will easily find them, likely in the first quarter. But they should also pay attention to their opponents' screening, because they do the same.

The difference between the Warriors and other teams is that when those off-ball illegal screens don't get called, they almost always result in a bucket because they have some of the best shooters in the planet. That's what really separates them from everyone else, not the nature of their screens.

As long as Stephen Curry and Klay Thompson make open shots, the illegal screen accusation won't die. That doesn't mean those accusations have any merit.

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Nobody can stop Golden State's deadliest play