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Ed Downs remembers the pivotal phone call that changed the game for Chris Bosh. It was on Saturday, July 12, and the Miami Heat star called his personal fitness trainer to tell him that, unlike his former teammate LeBron James, Bosh would be staying with Miami.

Five days before, the Houston Rockets had pitched the two-time champion and nine-time All-Star on a four-year, $80 million-plus contract to play a complementary role to two other stars, James Harden and Dwight Howard. Four days later, the Heat offered a five-year, $118 million max contract with a much different role. Bosh accepted.

"He said, 'Ed, my role is about to change, and it's going to be much more demanding,'" Downs recalled. "I think there was some disappointment about LeBron leaving, which motivated him to really want to prove himself this season. He felt, 'This is my time. Let me do what I did in Toronto.'"

That expanded role—which Bosh's agent, Henry Thomas, said was "a very significant thing for Chris" envisioned by Heat management during negotiations—is likely becoming the No. 1 option for the Heat, four years after Bosh held that position in Toronto. Still only 30 years old and coming off two healthy seasons, the opportunity to pick up on his past is there.

"I'm excited," said Bosh, who averaged 16.2 points in a career-low 32.0 minutes per game last season. "I really want to do it for the city of Miami—to show my evolution and my growth, and display a different level of my talent. It's not easy; I went from [about] 20 [points] and 10 [rebounds] in Toronto to 16 and 7 last season.

"I'm a much better player than I was in Toronto, and I'll be able to give Miami a lot more. I'm excited to really test out what I've done over these years, as far as leadership is concerned, as far as what's on the court is concerned, and really put it out there."

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Bosh's former Raptors coach Sam Mitchell believes the Heat's greater expectations for the versatile power forward, who's still in his prime, come with the financial territory. But based on his past success in Toronto and sacrifices in Miami, Mitchell said Bosh will excel as the likely focal point in the offense.

"Pat Riley gave him the contract that said, 'You're going to be the guy,'" Mitchell said. "People think Chris Bosh is not that guy. When the offense is running through him, they're going to find out, I guarantee you. One of those Big Three in Miami had to take a backseat and check his ego at the door. If Chris hadn't done it, they may not have two championships. Now, I think Chris is going to play even better than he did in Toronto. I really do, because now he has something to prove all over again."

Heat coach Erik Spoelstra also believes Bosh is ready for the challenge.

"CB is a true throwback, and he'll have to shoulder a bigger responsibility," he said. "But he's proven himself as a No. 1, No. 2 option, No. 3 option and as a two-time champion. So he'll figure out a way to help us win, and that's the most important thing. I just really respect Chris for not only his talent, but, more importantly, his versatility. Whatever is needed to help a team win, he's willing to do."

Getting to work

Knowing that he would be playing increased minutes and carrying more of the offensive load, Bosh told Downs after he signed that he essentially wanted to hire him full-time. Downs, who has trained other All-Stars such as Baron Davis, Jamal Mashburn, Alonzo Mourning and Dwyane Wade (who introduced him to Bosh), was on board.

After he officially signed with the Heat on July 30—he was traveling throughout Africa and Europe for most of the month—Bosh worked with Downs every week from then until mid-September. Downs said that represented a 30 percent increase in workouts from previous summers.

Downs also worked extensively with Bosh's personal skills coach, Miles Simon, a former star at Arizona and now a trainer for elite players as well as an ESPN college basketball analyst. Bosh would train for five to six days straight one week with Downs and Simon in the Los Angeles area—where the Heat star has an offseason home—and then travel to Miami the following week to train with Downs at his Elite Athletes Performance training facility.

Courtesy of Ed Downs

"I was just trying to maximize my potential on the basketball court," Bosh said. "This is a big season for me, and I want to show what I'm capable of. I don't think everybody has seen it. It was only flashes [in Miami]; they didn't think I could do it because they needed me to play off the ball."

Downs collaborated closely with the Heat, sending weekly reports with video clips to the team's longtime strength and conditioning coach, Bill Foran. He and Downs outlined a plan for Bosh to weigh 238 pounds with around 8 percent body fat before training camp began, so he would be better prepared for his bigger role from the start.

"He's accomplished those goals," Downs said. "And Bill's been very, very excited and happy."

Chris Bosh Season-By-Season Season Team MP FG% 3P% TRB AST STL BLK PPG PER 2003-04 TOR 33.5 .459 .357 7.4 1.0 0.8 1.4 11.5 15.1 2004-05 TOR 37.2 .471 .300 8.9 1.9 0.9 1.4 16.8 17.5 2005-06 TOR 39.3 .505 .000 9.2 2.6 0.7 1.1 22.5 23.2 2006-07 TOR 38.5 .496 .343 10.7 2.5 0.6 1.3 22.6 22.6 2007-08 TOR 36.2 .494 .400 8.7 2.6 0.9 1.0 22.3 23.8 2008-09 TOR 38.0 .487 .245 10.0 2.5 0.9 1.0 22.7 22.1 2009-10 TOR 36.1 .518 .364 10.8 2.4 0.6 1.0 24.0 25.0 2010-11 MIA 36.3 .496 .240 8.3 1.9 0.8 0.6 18.7 19.4 2011-12 MIA 35.2 .487 .286 7.9 1.8 0.9 0.8 18.0 18.9 2012-13 MIA 33.2 .535 .284 6.8 1.7 0.9 1.4 16.6 20.0 2013-14 MIA 32.0 .516 .339 6.6 1.1 1.0 1.0 16.2 19.0 Basketball-Reference.com

Compared to last summer, when the Heat wanted Bosh to gain weight to play center, especially for defensive purposes, this time around the emphasis was on leaner muscle. So Bosh worked with his personal chef, Terrance Williams, to increase his calorie intake and follow a high-protein diet with lower carbs. "He has more strength, endurance and speed," Downs said.

For the second straight summer, Bosh also didn't play pickup ball in order to preserve his body after four seasons of playing into June. He returned to the Heat practice center last week and has been regularly scrimmaging with the team since in anticipation of the opening of training camp on Sept. 27.

So what was the summer like for Bosh? Downs and Simon offered a glimpse inside a typical week in L.A.:

Almost every morning, Bosh left his home nestled in the mountains of Pacific Palisades to arrive by 10:30 a.m. at UCLA (or Pepperdine on one occasion)—where the school arranged private court time for him with Downs and Simon. Some days, Downs would take Bosh to the beach by his house or Palisades Charter High School's track or football practice field beforehand for 4.5 total miles of running and plyometrics.

Courtesy of Ed Downs

The track sessions (completed with a 300-yard shuttle run) were designed to feel like the distance that Bosh might run each game in his new role, and for him to build up enough endurance to last through the fourth quarters of games. On other days, Bosh would run 10 reps of 80 yards on the hill outside of his house.

Once on the court, Bosh started with a 10-minute warm-up involving plyometrics, some with resistance bands. Two key exercises included sharpening his first step with additional resistance and improving his quickness with an agility ladder. Then Simon took over, starting with ball-handling before moving into either an inside or outside shooting routine for the majority of the session.

For Simon to know what to focus on with Bosh—they first met in 2011 through a Nike recommendation—the Heat star relayed notes from Spoelstra highlighting the main areas on the court he's going to catch the ball. In the past, the emphasis was more on perimeter shooting, so the lanes were open for James to drive and kick. As evident in his numbers, Bosh made more three-pointers last season (74 at a respectable 33.9 percent) than he did in all of his seven years in Toronto combined.

This time, the direction from Spoelstra was mostly 17 feet and in, including the blocks, elbows and mid-post. The bottom line: less jump-shooting and more attack moves. Simon predicts that as the main weapon, the 11-year veteran will get about five more shot attempts (up from 12.1 last season) and about five more free-throw attempts (up from 3.4, the lowest in his career) than he did last season.

Simon noted that because Bosh is left-handed, he's been more comfortable in his career on the right block shooting turnaround jumpers over his left shoulder, which is why the two worked to improve Bosh's skills on the left block at UCLA. Only once in his four seasons with the Heat (in 2013-14) did Bosh shoot better on the left side of the court than the right (44.5 percent vs. 42.5 percent, according to Vorped.com).

For those low-post situations, Bosh worked on his footwork, right-hand dribble, jump hooks, turnaround jumpers and counter moves. One included attacking off the dribble to the middle of the paint, and then spinning back the other way to finish with a jump hook.

Courtesy of Miles Simon

"Chris has incredible touch on all of his shots, whether it's facing up, jump hooks," said Simon, who has also trained Klay Thompson and coached at James' and Kevin Durant's Skills Academies. "I think you'll see his right hand be a little bit more effective. That's something he's been working on over the last couple years."

Simon focused each workout to one area of the floor on a given day to stress efficiency. On the following day, the emphasis might have been the elbow area for high-post entries and face-up moves, like driving into the paint for a long layup, or a two-dribble move into a turnaround jumper. They also worked on the two-man game and dribble hand-off action. Sometimes Simon brought in other players, such as ex-UCLA big men (and Simon clients) David and Travis Wear.

When Simon was done with his part, lasting more than an hour, Downs stepped in again to carry out certain exercises that mimicked his actual on-court movements to boost performance. For example, in one low-post drill simulating backing down an opponent, Bosh had resistance bands with additional force attached from his wrists to his ankles so he would feel more pressure—translated to a double-team in a game—when making a move.

Some days instead of staying at UCLA, they went back to Bosh's house, where Downs helped design a customized gym geared toward "stabilizing his hips to prepare for when he's backing down someone or playing defense, improving his strength and flexibility to be able to take a hit while going up for a dunk or making a block, and adding to his explosive rotational power for things like dunks and turnaround jumpers."

Courtesy of Ed Downs

"You'll probably see more dunks and rebounds this year," said Downs, a former trainer to Navy SEALs and a fifth-degree black belt who also had Bosh do martial arts for strength training and mental toughness. "I'm talking about Darius Miles-type dunks. He used to watch him and liked his dunks. Overall, Chris will be a lot more aggressive. When you have to divert to LeBron or Wade, I think it calls for a little hesitation. Now he's going to have plays run for him."

Though not under contract with the Heat, Downs will continue to meet with Bosh in Miami regularly throughout the season. And because of Bosh's bigger role, Downs will travel to meet with the big man on the team's Midwest and West Coast road trips.

"It's to help maintain his proper conditioning, strength training and flexibility," Downs said. "We want to make sure physically he's not breaking down with the extra minutes."

Some snippets below from Bosh's summer training (in order of a typical daily routine):

Taking the court

To envision Bosh this season, think a bit of how Dirk Nowitzki is used in Dallas. In fact, after the Heat lost to the Mavericks in the 2011 Finals, Bosh couldn't get his mind off of the future Hall of Famer, who averaged 26.0 points per game in the series. That still holds true today.

"Going back to that first summer [we worked] together, he used to just flip open his computer at breakfast—after they had just lost to Dallas—and he was watching Dirk Nowitzki and some of the stuff that he did in the high post and the long-post area," Simon said. "He studies a lot of film, he's super knowledgeable."

"You will see a little bit of Dirk from Chris this season," Downs said. "And don't think [the Finals loss] hasn't crossed our minds when I'm training him. He's using more balance and coordination, and turnaround fadeaway jumpers. Remember the move that [Jamal Mashburn] would do? Shoulder fake, turnaround. That could be a go-to move for Chris, kind of like Dirk does, too."

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An NBA scout who was in Toronto when Bosh was identified the forward's sweet spot as the right elbow extended, where he liked to shoot a one-dribble pull-up. While then-coach Jay Triano largely posted up Bosh—35 percent of the time in 2009-10, according to Synergy Sports (subscription required)—his predecessor, Sam Mitchell, put him in more face-up opportunities in the mid-post.

"As Chris progressed, his face-up game and free-throw game got better, and his rebounding game also got more confident," the scout said.

"I think [the Heat] will try him with any number of different looks," said longtime NBA scout and consultant Chris Ekstrand. "They'll try getting the ball to him in the high post. He's a pretty good passer. If they have a matchup they like, he'll be posted up on the block. These days, there are fewer of the true seven-foot, 250-pound guys playing defense in the post, so there are going to be nights where there are options for him to get the ball in a traditional low-post role. But he's a guy that has a reputation now for being able to make threes. If people don't press up on him, he'll make it.

"He's a bona fide threat, compared to when he was in Toronto. The more diversified your offensive attack is, the more effective it is. And I think he's a guy who can score from almost anywhere on the court. He's a very, very good player. Sometimes people forget how good this guy is."

Mitchell said Spoelstra should ask Bosh to give him his favorite plays from his Toronto days, so he can look to add a variation on them. That's important, to Mitchell's way of thinking, because a coach needs his top scorer to feel the most comfortable in the offense. While Bosh should get a handful of face-up opportunities, there's also reason to believe that Spoelstra's offense won't be isolation-dominant after the Spurs burned the Heat with an abundance of movement.

And if that's the case, Bosh still looms as the crux of the Heat attack.

"He knows how to get open without the ball better than he did when he was in Toronto," Ekstrand said.

Defensively, while the Heat will miss James' swarming nature, they still have, in many respects, their middle linebacker in Bosh, whose main job was to hedge on pick-and-rolls and then quickly rotate back to be the paint protector. He did it masterfully with his lateral footwork, 7'4" wingspan and basketball IQ, and by last season's end, he was the best pick-and-roll defender in the NBA, holding big-man opponents to just 0.531 points per play, according to Synergy Sports. Also consider this: Bosh's plus-5.6 plus-minus was the best mark for any player on the team, even better than James.

Still, Bosh knows some adjustments will be needed.

"We're still athletic, but not as athletic, of course, because of LeBron [leaving]," Bosh said. "We don't have that guy just in the woods playing safety, getting his hands on a lot of balls. I think team-wise we have a lot of rugged, rough defenders that are not going to give in easy, and that's what it's all about. It's about resistance. It's a very talented league and guys are going to score; you just want to make it as difficult as possible.

"We've got to bring that defensive-first mentality back—not that we didn't have it, but it kind of slipped away and we want to really tighten it back up and get stronger."

There's some promise: The Heat now have one of the best swingman defenders in the league in Luol Deng, an emerging stretch 4 (and willing defender) in Josh McRoberts and many of the team's championship-experienced players are returning. Most important, Bosh is optimistic about Wade's health and how much he can contribute this season.

"It's on [Wade and I] and pushing guys and pushing ourselves, getting everything we can out of each other," Bosh said. "We don't have a long time to play this game; we're on the latter ends of our careers. But this is a time for us to really show what we've got."

A new day and age

Mitchell, who coached Bosh starting in his second season, remembers a time when the No. 4 overall draft pick from 2003 wasn't ready to be the leading man.

"It took Chris a little while to grow into that role and accept that responsibility, but once he did, he embraced it," Mitchell said. "I don't think it's going to take him any time to set the tone. When he walks in the door, his teammates are going to know, because of the contract and what he's done, he's the man. And I'll tell you what: He is an unbelievable leader."

Steven Freeman/Getty Images

Even off the court in the past year or so, Bosh has carved his own lane. He's encouraged students to learn computer code, showed off his acting skills on a variety of TV shows—including Hell's Kitchen, Jessie, Law & Order, Parks and Recreation and Tall Justice (he filmed Part 2 recently)—and earlier this month, he launched his own line of ties during New York Fashion Week called Mr. Nice Tie.

From fashion design to his tenure in Miami, Bosh has played well against expectations. How often do you hear of an All-Star, healthy and before his prime, changing teams to become a complementary player?

Now ask yourself this: How often do you hear of that kind of player re-emerging as a go-to threat, and leading his team to a title?

"Can we be championship contenders? Absolutely," Bosh said. "But can we just settle and be like a four, five, six seed? Yeah. We want to do what's difficult, and we're going to go out there and make it happen."

Jared Zwerling covers the NBA for Bleacher Report. Follow him on Twitter and Instagram.