With injuries to Russell Westbrook and Derrick Rose dramatically weakening two of their biggest challengers, there aren’t many obstacles left in the path of the Miami Heat.

After a methodical sweep of the Milwaukee Bucks in the first round, their playoff record is now 26-7 with the Big Three in the starting line-up. In a league becoming more perimeter-oriented, the Heat have the ultimate small-ball frontcourt, with Chris Bosh and Shane Battier spacing the floor for LeBron James. You can’t defeat Miami by playing their game, which is why the massive front-lines of the Indiana Pacers and Memphis Grizzlies are the biggest threat to the NBA’s newest dynasty.

While most of the league zigged, the Pacers and Grizzlies zagged. Instead of moving towards a four-out offense that spaces the floor for pick-and-rolls and dribble penetration, they run their offense through two skilled big men in the post. As a result, they have remarkably similar rosters and styles of play. They prefer to operate in the halfcourt, pounding the ball inside and grinding out possessions defensively. Even more intriguingly, they both face a challenge in the second round that could prepare them for the Heat: a clash of styles against the second (Kevin Durant) and third (Carmelo Anthony) best small-ball 4’s in the NBA.

A generation ago, most front-lines looked like Zach Randolph/Marc Gasol and David West/Roy Hibbert. Randolph (6’9 260) and West (6’9 250) are two of the toughest power forwards in the NBA, old school players who can brutalize smaller defenders on the block as well as step out and knock down a 15-foot jumper. Gasol (7’1 265) and Hibbert (7’2 280) are two of the league’s biggest centers, defensive anchors who can control the area around the rim and protect it at an elite level. While none of the four have three-point range, they know how to play off each other and create space while operating in the narrow confines of the paint.

With so much size upfront, it’s no surprise Indiana and Memphis are two of the slowest teams in the NBA. In the regular season, the Grizzlies averaged 88.4 possessions per-48 minutes, 30th in the league, and the Pacers averaged 90.2 possessions per-48 minutes, 25th slowest. That continued in the first round of the playoffs, with Memphis/LA Clippers and Indiana/Atlanta turning into half-court rock fights. Both teams dictated the style of the game: the Grizzlies never allowed the Clippers to get out into transition while the Hawks were forced to abandon their small-ball front-court and start Johan Petro by Game 3.

As the Knicks and the Thunder discovered in Game 1 of the second round, it’s hard to go small against power forwards as skilled as West and Randolph. New York only has two conventional big men (Tyson Chandler and Kenyon Martin) left on their roster and they prefer to use Carmelo at the 4. The problem is that leaves either Carmelo or Iman Shumpert giving up a lot of size against West, who had 20 points on 8-for-15 shooting in Game 1. And while Oklahoma City starts Kendrick Perkins and Serge Ibaka, playing both at the same time dramatically impacts their floor spacing, since other teams don’t have to defend Perkins.

The key is to attack the Pacers and Grizzlies where their size can be negated: in transition and when they go to their bench. Forcing live-ball turnovers against both is crucial, since that speeds up the tempo of the game and creates open-floor scoring opportunities. And when their big men are fatigued or in foul trouble, the opposing team has the opportunity to dictate the style of the game. The Pacers went 12 minutes without both Hibbert and West on the floor in Game 1; the Grizzlies went 14 without both Randolph and Gasol. The Thunder and the Knicks have to take advantage of the stretches of the game when they can go small with impunity.

Those stretches are where Indiana (Danny Granger) and Memphis (Rudy Gay) miss their leading scorer from last season. This season, Granger played in only five games due to a knee injury, while Gay was dealt in a salary-cap move at the trade deadline. There are plenty of differences in their games, but both are 6’9+ forwards capable of playing inside and out. Without them, neither the Pacers nor the Grizzlies can put too much firepower on the floor in the rare occasions when they go small. When Randolph was in foul trouble in their first two games against the Clippers, it was a completely different series.

Where the two teams differ is how they’ve adjusted without Gay and Granger. Indiana has run more of their offense through Paul George, their 6’8, 220 small forward. George, who won the Most Improved Player award this season, has thrived in Granger’s absence, averaging career-highs in points, rebounds and assists. Memphis, in contrast, has turned the keys over to Mike Conley, their 6’1 185 point guard. Conley is now their best shot-creator and the player they turn to in end of the clock situations. He went toe-to-toe with Chris Paul in the first round and they’ll need him to dominate his individual match-up against the Thunder, especially with Westbrook out.

If either Memphis or Indiana can get out of the second round, it will have been the perfect warm-up for an eventual series against Miami. For the most part, the Heat do everything the Thunder and the Knicks do, they just do those things better. If the Pacers let J.R. Smith and Carmelo Anthony take over the game from the perimeter, they will have no chance against LeBron James and Dwyane Wade. And if the Grizzlies can’t contain Kevin Durant when Ibaka or Nick Collison is the lone big man on the floor, good luck handling LeBron when Bosh is spotting up for corner 3’s.

Most importantly, if Memphis and Indiana can’t dictate the match-ups in the second round, there’s no way they’ll be able to do so against Miami. In the three years since “The Decision”, only one team -- the 2011 Mavericks -- has forced the Heat to stay big. Against everyone else, Miami’s postseason record with their Big Three healthy is 24-3. A generation ago, “small-ball” was an underdog strategy, a desperate attempt to even the playing field in a sport dominated by centers. That’s how much the balance of power has changed: in 2013, Goliath is the underdog.