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Erik Spoelstra coached the Miami Heat to four NBA Finals appearances and two titles in his first six seasons at the franchise’s helm. And this is where the hard part begins.

With LeBron James—the best basketball player on the planet—headed back home to the Cleveland Cavaliers, Spoelstra will face a mammoth challenge in the coming months and years. He has to reinvent an entire system.

LeBron was central to everything the Heat did on both ends of the floor. It was his freaky athleticism and ability to guard multiple positions that allowed Miami to play the hyper-frenetic trapping defense which became its calling card during its mini-dynasty. Similarly, it was his multidimensional offensive game—and particularly his dynamite work in the low post—that served as the foundation of Miami’s uber-efficient space and deface O.

This is the paramount problem Spoelstra will grapple with in 2014-15 and beyond: How do you replace the irreplaceable? It’s what undergirds every other challenge he and the Heat confront as they attempt to win their fifth consecutive Eastern Conference crown.

Including…

1. Deploying Chris Bosh

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Bosh was a superlative supporting player for Miami during its title run—a perfect fit alongside James and Dwyane Wade.

The crux of Bosh’s value was his ability to knock down mid-range shots. Since 2005-06, according to Basketball-Reference, the big never shot below 41.1 percent from 16 to 23 feet. Remarkably, he’s shot better than 45 percent in six separate seasons and hit on 52.9 and 48.7 percent of his attempts the last two years.

Bosh’s mid-range prowess pulled opposing big men toward the perimeter, which cleared room for James and Wade to wreak havoc inside.

The problem, though, is this: Mid-range shots, in a vacuum, are the least efficient in basketball. Jump shots are fine when they’re a means to an end, but Spoelstra probably isn’t interested in an offense that’s built around Bosh shooting 18-footers.

Spo, then, will likely have Bosh spend more time down low and outside the three-point line—more efficacious locations. And it’s a good bet he will do well there. The big hit 33.9 percent of his career-high 218 three-point attempts in 2013-14 and, according to NBA.com, finished fourth in the Association in field-goal percentage from within five feet.

“I think sometimes you miss it,” Bosh told ESPN’s Tom Haberstroh when asked about the appeal of returning to a No. 1 scorer role. “You wonder if you can still do it and step up to the challenge.”

If Bosh can't step up, Spo will have to give him a boost.

2. Prolonging Dwyane Wade’s Usefulness

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The Heat were very cautious with Wade last season. The increasingly brittle guard sat out 28 games in the regular season and, when he did suit up, played a career-low 32.9 minutes a night.

Going without your second-best player with that kind of regularity is easy when you’re playing for the postseason and are effectively guaranteed a top-two spot in your conference, but it might be tricky for a fringe playoff team. If the Heat are jockeying for, say, home-court advantage in the playoffs, will they be as willing to rest Wade?

Spoelstra will have to toe a very fine line in his handling of Miami’s franchise player.

3. Helping Shabazz Napier Get His Groove Back

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Napier seemed, from all indications, to be ready to step into the NBA and contribute right away. He’s 23 years old—seasoned for a rookie—and was dominant in college. Not only did he lead UConn to a national title in the spring, but he paced the NCAA in win shares during 2013-14, according to Sports-Reference.

But then the Summer League came. Napier was dreadful in both Vegas and Orlando, shooting 27.7 and 27.3 percent from the floor in the two tournaments.

With LeBron absent, Napier, even as a rookie, will be expected to contribute as a scorer in Miami. Spoelstra will need to arrest Napier’s slide.

4. Solving Luol Deng

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Deng is a plus defensive player who spent his formative years in the Chicago Bulls' winning program. In this sense, he’s a great replacement for LeBron. But he’s also a wildly different player than James, and the swap creates some interesting issues Spoelstra will have to massage.

For starters, while Deng excels defensively, he’s a much more conventional stopper than the departed star. While LeBron can guard multiple spots, Deng is simply an aces perimeter defender. This will make it difficult, if not impossible, for Miami to play the trapping style that’s come to define it.

He also creates some issues offensively.

While Deng is a reasonably efficient scorer—according to Basketball-Reference, his career true shooting percentage of 52.5 is just a tick below the 53.7 that average small forwards post—he’s not much of a shooter. Deng connected on just 30.2 percent of his three-point attempts in 2013-14. This could be a problem when he’s paired with Wade, a career 28.9 percent three-point shooter.

One potential solution to this spacing concern could come from Josh McRoberts. The offseason signing has unusual range for a power forward—connecting on nearly 37 percent of his triples for the Charlotte Bobcats a season ago.

It's a wholly strange situation, though. In lineups where Bosh, McRoberts, Wade and Deng are all on the floor, Miami will have better shooters at the 4 and 5 than it does the 2 and 3. Spoelstra will have to make it work.

A Nimble Thinker

But as difficult as these challenges may be, they’re problems Spoelstra is well-equipped to solve. He’s shown himself to be an intelligent and nimble thinker. Constantly in pursuit of new edges and different ways of coaching the sport, this pursuit of knowledge has led him, among other places, to the gridiron, where he watched Philadelphia Eagles coach Chip Kelly run one of his innovative practices last summer.

Suffice it to say, he's an outside-the-box cogitator. Consider the praise Sports on Earth’s Sean Highkin lavished on him during the 2014 playoffs:

Spoelstra's genius lies in his understanding of the fundamental differences between matchups, a belief in fluidity and adjustment over dogma. He's unafraid to tinker with his rotations, yanking players who have started all season out of the rotation for games at a time, and creating a culture where everyone understands that they still need to stay ready.

Genius. It may be a bit hyperbolic, but it’s an expression that’s often used in association with the coach. While Miami’s twin titles are generally—and correctly—attributed to the tremendous talent those Heat teams possessed, they’re also a function of the strategy the coach concocted. The Heat didn’t really become the juggernaut we knew and loved (or loathed) until Chris Bosh went down with an injury during the 2012 playoffs and Spo started playing LeBron at power forward—jump-starting an era of small ball and big wins for Miami.

While he won’t have the caliber of component parts to work with this coming season, with that kind of inventiveness and appetite for schematic risk, it’s possible Spoelstra could whip his Heat into a threat in the still-gimpy East.

It would be a step back for a franchise that’s become accustomed to contention, but it would mark a step forward for a coach that’s developed a reputation for getting the best out of his roster.