Chris Bosh is key to the Heat's pick-and-roll defense

Defense is a curious thing to track in the NBA. While offense can be cranked down to shot distance, type and whether it was assisted, there's no easy way to track what a player does on defense. It mostly needs to be seen with the eyes as you watch a team's five-man unit either make crisp rotations or allow silly mistakes because of a lack of awareness.

There's something to be said about a team having a defensive "identity." If a team knows what it is trying to accomplish on defense, it knows how to perform as individuals and as a group. It comes as no surprise that a team like the back-to-back champion Miami Heat allowed the fifth-fewest points per game last season.

They ranked first in two specific categories, though, and they go hand in hand: pick-and-roll, ball-handler defense and pick-and-roll, roll-man defense, per Synergy Sports Technology. The Heat were a team that committed to double-teaming the ball-handler on pick and roll, a high-risk strategy with a very slim margin for error that aims to disrupt a play's timing and cause turnovers. (In NBA vernacular, this is known as "blitzing" the pick and roll). It requires aggressive traps and crisp rotations from everyone involved, but the big man who has to step out to the perimeter to apply pressure is especially important. The success of that step of the process can make or break the strategy.

This is where Chris Bosh proved to be critical for the Heat.

Miami's pick-and-roll looks something like this in its simplest form. Here, Carlos Boozer sets a screen for Nate Robinson. Bosh doesn't sit back to contain the ball-handler and instead steps in front of Robinson, which is known as hedging:

Often times, a defense will sit back and allow the point guard to drive into the big man sagging in the lane. But the Heat prefer to force the ball-handler to actually make a play against tight defense while the other defender (here, Mario Chalmers) recovers or traps.

Once Bosh has forced Robinson around his hedge, he rotates back to Boozer:

Chalmers is lined up with Robinson and Bosh is back within reach of Boozer. The speed of Bosh has therefore allowed the Heat's coverage of this pick and roll to be successful.

Video of the play:

The risk involved is straightforward: if two players cover one player, another player is open. It takes not only precise timing but great mobility to recover as a trapping big man. Bosh is great at this.

Here, Luke Babbitt sets a screen for Damian Lillard. Bosh and Chalmers trap Lillard while Babbitt spots up along the arc. The Heat are now blitzing Lillard:

Bosh slides toward Babbitt, but keeps his head turned toward Lillard. Lillard passes to Babbitt, but Bosh easily recovers, challenges and forces a miss:

Video of the play:

It was an easier play than normal for Bosh because Babbitt was not a threat to drive from the perimeter. He didn't distance himself far enough away from Lillard and Lillard didn't help by driving toward him.

That is not always the case, though. Here, Bosh steps out to blitz Jeff Teague while Josh Smith pops to the perimeter.

Bosh pokes the ball away from Teague but he recovers. This has created a great deal of ground for Bosh to cover as he bolts back to Smith.

The opposite of what happened above with Lillard and Babbitt has occured in this play. Bosh was pulled in the opposite direction of the roll man, and Smith doesn't shoot a three:

Nevertheless, Bosh still makes it back in time because of his speed returning to his man after helping on Teague. He shuffles to the rim with Smith, who misses the shot:

Video of the play:

That type of mobility and decisiveness allows the Heat to blitz pick-and-rolls. Few players at any position, let alone frontcourt players, can cover the kind of ground Bosh can:

The goal is to force turnovers from bad passes or steals because of two defenders applying pressure. Miami defended 1,270 pick-and-roll plays last season (ball-handler and roll-man combined) and a total of 8,362 field goals, according to Synergy Sports Technology. The team had 710 steals and forced 1,280 turnovers, and it's likely many were forced out of pick-and-roll situations. That's because Bosh was constantly rotating and making split-second decisions on defense.

But the Heat -- and Bosh's -- execution of their defensive strategy disrupted timing even without getting steals. The following play is a good example of a successful blitz without a turnover involved. Richard Hamilton takes a screen from Boozer and is funneled into the corner by Bosh:

This is the "danger zone." Boozer is at the elbow and has a defender covering him, which is fine. The Bulls have two players behind the arc on the opposite side, though, one of whom is a single pass away if Hamilton can get the ball to Boozer:

The corner trap from Bosh and Ray Allen does enough to deter a clean pass to Boozer and he catches the ball behind the arc, where he is not a threat. The Heat are still in a tight spot, though, as Bosh needs to recover in time to defend Boozer if he pulls up for a mid-range jumper or tries to drive. Norris Cole and Dwyane Wade need to be able to close out on either of the Bulls' spot-up shooters if Boozer passes and cannot help Bosh's rotation:

But because of his speed, Bosh is able to get back in time and contests the shot. Boozer misses:

Video of the play:

Here's another example of Bosh making multiple defensive rotations while blitzing pick-and-rolls:

If the roll man isn't a perimeter player and is an at-the-rim finisher, this presents another problem. The blitzer needs to be able to rotate back to the roll man in time for his help defender to rotate out to the perimeter, because it's likely his man is spotting up on the perimeter.

Here, Dwight Howard sets a screen for Steve Nash and rolls to the paint:

Bosh and Chalmers trap Nash. As Rashard Lewis rotates into Howard's clear path to the rim, Earl Clark shifts to the top of the break to help Nash. This is where the Heat's scheme can be exposed. Lewis can't leave Howard to cover Clark, so a shooter should be open if Nash can get rid of the ball.:

But two things occur here that make this sequence successful for Miami:

• The pressure applied to Nash by Bosh forces a bounce pass that was barely catchable near Clark's feet. This gives Lewis enough time to rotate off of Howard and out to Clark.
• The only reason this doesn't create a defensive breakdown is because Bosh quickly recovers after the trap by running directly in front of Howard to stop the entry pass. Lewis is then able to rotate to Clark because Bosh was already recovering:

Video of the play:

Here's the exact same sequence, but with the Sacramento Kings and DeMarcus Cousins:

Blitzing a pick and roll is dangerous, but with Chris Bosh crisply rotating around the court, it becomes organized chaos. That's how the Miami Heat can be a lockdown defensive team without a traditional center.