Five reasons the Miami Heat won't three-peat

What is it about today's NBA that makes the three-peat so difficult to complete? There are several reasons why over a decade has past since the last time a team won three NBA championships in a row, one of course being the expanded postseason. Back in the late '50s and early-60s, when the Boston Celtics won eight championships in a row, there were fewer rounds in the postseason and less teams in the league.

When the Celtics won their third championship in the row during the 1961 season, they had a much easier road to the promise land than what teams have to go through in the modern era. To get to the 1961 NBA Finals, Boston only needed to get past a divisional semifinal round and then the division finals.

In the modern era, just three teams -- the Chicago Bulls twice in the '90s and the Los Angeles Lakers in 2002 -- have three-peated because the postseason is essentially a crapshoot. The best teams in the league are going to get to the playoffs, but upsets are bound to happen due to the four-round system. Here's a look at five reasons why the Miami Heat are going to have a tough time completing the first three-peat since the early-2000s:

1) Wear and tear: Physically and emotionally, it's a drain on the body and mind to deal with the pressure of winning an NBA championship. It's a long, grueling season, and LeBron James is human just like everyone else. James, 29, is still in his athletic prime, but he's being counted on to carry the Heat, night in and night out. He's put a lot of wear on his body over the past few NBA seasons, and it's going to be absolutely exhausting trying to reach the finals for the fourth straight year.

2) Four-round playoff system: Will the NBA ever have another dynasty like the 1960s-era Boston Celtics, a squad that won 11 championships in 13 seasons? Probably not, and that's because teams back in those days needed to only get through three rounds to win a title. The additional round that teams must win in the modern era makes the postseason far more of a crapshoot than it was 50 years ago.

3) Complacency: After winning two championships in a row, are the Heat still hungry? James already got the monkey off his back by winning his first title in 2012, and he earned another championship for Miami last season. It's human nature to lose a bit of drive and intensity after so much success.

4) Age: The Heat's age factor can't be ignored. Dwyane Wade is 32, Chris Bosh just turned 30 and Ray Allen is 38. Father Time is going to catch up to them, eventually. They'll try to stay fresh through the postseason, but it doesn't get easier when you're on the wrong side of 30.

5) Los Angeles Clippers and a solid West: With all the madness surrounding the Donald Sterling scandal, the Los Angeles Clippers have become a team that America is rallying behind. The additional fan support and media frenzy might give Los Angeles an extra little boost as the postseason continues. But even if the Clippers don't make it to the finals, the Heat's potential opponent from the West will be strong. The San Antonio Spurs, a perennial championship contender, are still in the mix, and the dangerous Portland Trail Blazers are also still alive. Perhaps even more of a threat to James and company is Kevin Durant and the Oklahoma City Thunder.