The Chicago Bulls had the best record in the NBA under first-year head coach Tom Thibodeau. Of their top eight players in terms of minutes played, only one (Keith Bogans) was over 29-years-old last year. They had the best defensive rating in the NBA, as well as the league’s 22-year old MVP.

It’s a formula that should ensure multiple trips to the NBA Finals, except for one problem – the Miami Heat. Even without home-court advantage, the star-studded Miami roster beat Chicago 4-1 in the Eastern Conference Finals, exposing some holes the Bulls will need to address to become champions.

Chicago’s defense starts up front, with three of the best rim protectors in the NBA: Joakim Noah, Taj Gibson and Omer Asik. But while all three blocked over 3.5% of the other team’s field goal attempts in their time on the floor, Carlos Boozer, the other big man in the Bulls rotation, had a minuscule block percentage of 0.7%.

Boozer, an undersized 6-foot-9 power forward without much lateral mobility, was the weak link in Chicago’s defense last year. When he was on the court, the Bulls gave up 104.6 points per 100 possessions; when he was off, that number improved to 98.1.

He’s unable to match-up with elite power forwards like Chris Bosh, and he’s not very effective as a help-side defender either. That’s a huge problem for Chicago’s team defense, which depends on long and athletic big men. The Heat routinely attacked Boozer in pick-and-rolls, to the point where the Bulls often made offense/defense substitutions at the end of the game to keep him off the floor defensively.

Managing Boozer’s minutes in the ECF became a tough choice for Thibodeau: for all his defensive weaknesses, he was nearly indispensable to Chicago’s offense in the series. Boozer is the only other member of the Bulls who can consistently create his own shot beside Derrick Rose. In the regular season, Boozer and Rose had usage ratings of 26.9 and 32.2 respectively, while none of the other rotation players had usage ratings over 22.0.

Rose won the MVP award not because he “carried” the rest of his team, but because he was such a dominant scorer that the Bulls could leverage his offensive ability by sacrificing offense at the other four spots on the floor. Line-ups featuring Rose and four of Chicago’s defensive-minded players were almost impossible to score on, and the 5-man unit of Rose, Bogans, Luol Deng, Gibson and Asik had the highest defensive rating in the NBA.

At 6-foot-3, 190 with a blinding-fast crossover, a max vertical of 40 inches and turbo jet speed, Rose became nearly indefensible when he added an outside shot last year. He shot 33% from 3-point range and went from taking less than one a game to nearly five. After the first round of the playoffs, he left Indiana Pacers head coach Frank Vogel in awe: “He’s got Iverson’s speed, Kidd’s vision, Billups’ shooting and Jordan’s athleticism. How do you guard that?”

The Heat answered Vogel’s question two rounds later, when they put a 6-foot-9, 270 forward with a 7’0 wingspan on him. In shutting down Rose in the fourth quarter throughout the series, LeBron James displayed his own unfathomable physical gifts: he’s got six inches and over 60 pounds on Rose, yet he’s somehow just as fast. Rose couldn’t get around him and was forced to repeatedly take step-back jumpers over a leaping 6’9 defender, which is a low-percentage shot for anyone not named Dirk Nowitzki.

Such a dramatic defensive cross-switch should have created mismatches for Chicago’s other perimeter players, but none of them were capable of consistently exploiting the defense of Mike Miller or Mario Chalmers. Kyle Korver and Bogans are one-dimensional jump shooters while Ronnie Brewer can’t shoot at all.

The real disappointment was Luol Deng, who averaged 17 points on only 42% shooting in the series despite all the defensive attention Rose received. Deng, a 6’9 220 small forward, is a solid two-way player but he’s never quite lived up to the expectations of his 6-year $71 million contract. With a career usage rating of only 21.6, he gets a lot of his points playing off the ball and isn’t the type of player you can run your offense through.

As a result, with Rose struggling to create good shots and the Bulls unable to take Boozer out of the game, Chicago was outscored 90-65 in the fourth quarters of Games 2-5.

A second shot-creator from the perimeter would ease the pressure on Rose. The Bulls needed him on the floor to stay competitive offensively; he played every minute of the second half and overtime in their Game 4 loss, with fatigue undoubtedly contributing to his offensive struggles.

The two biggest names on the free agent market are Jamal Crawford and Jason Richardson, but neither will come cheap and it’s unclear whether there will still be salary-cap exceptions to sign players of their caliber in the new CBA.

The trade market will be equally tricky. If they don’t want to weaken their strengths (Rose’s offense and their big men’s defense), the only players the Bulls can offer are Deng and Boozer, and there won’t be many teams willing to eat either player’s contract. One intriguing possibility is dangling Nikola Mirotic, a 20-year 6’10 Serbian sharpshooter who Chicago shrewdly picked up at the end of the first-round. Mirotic would have been a lottery pick were it not for a hefty buyout from his club team that will keep him in Europe for a few years.

To defeat Miami, the Bulls will have to score while keeping Carlos Boozer on the bench. And if they can’t add another perimeter shot-creator, their title hopes will come down to whether Derrick Rose can out-duel LeBron James in the fourth quarter of a deciding playoff game.