The last line of defense, shot-blockers are the most essential part of an NBA defense.
Without a competent shot-blocker, you're going to encounter teams that will do nothing but try to relentlessly exploit your weakness in the middle. If there's no shot-blocker in the middle, expect a lot of work to be done on defense because you're going to have to make up for the shortcomings of having a center who can't deter the high-percentage shots.
What that leads to is packing the paint. Once you start packing the paint, teams will start shooting from the perimeter. It becomes pick your poison, as you either run the risk of constantly giving up shots near the rim or allowing the opponent to get into a rhythm because of the number of open shots you're giving it.
That's why it's great to have a player who can always provide the threat of sending back a layup or dunk. You have one or two guys who can protect the paint, while the rest of the team spends time defending the perimeter. Having that big-time shot-blocker changes the entire outlook of the opposition as it looks for new ways to score without having to come face-to-face with said shot-blocker.
That's why a team like the Orlando Magic has made it to the NBA Finals or why the Dallas Mavericks won last year's championship. They had centers who were notorious shot-blockers and defenders. Having that post player who can completely affect the outcome of a game thanks to his shot-blocking prowess alone is one of the most valuable commodities you can have in the NBA today.
We take time to celebrate these players by naming the five most intimidating shot-blockers currently in the NBA, in no particular order.