Hand-checking: "A defender may not place and keep his hand on an opponent unless he is in the area near the basket with his back to the basket. A defender may momentarily touch an opponent with his hand anywhere on the court as long as it does not affect the opponent’s movement (speed, quickness, balance, rhythm)."
From its inception by Dr James Naismith to the beginning of the 1990s, the game of basketball was properly referred to as 'a big man's game'. The sport's record books, greatest dynasties, and top players tended to be athletes who towered over the sport.
Even players like Oscar Robertson and Magic Johnson, who were never the tallest men on a basketball court, towered over their guard position and gave the game the idea of a ball handler the size of a power forward.
However, the 1990s had two earth moving events that changed that prehistoric idea: First was the Chicago Bulls dynasty, led by the two wing players in Michael Jordan and Scottie Pippen. That brought the idea of the big man's importance to question, but it didn't exactly kill it. Right after the dynasty ended, the league became the walking ground for the Tim Duncan San Antonio Spurs and the Shaquille O'Neal Los Angeles Lakers.
The NBA landscape changed in 2004 when the game completely whipped its hands of hand-checking. This had been a form of defense primarily used on ball handlers to control their movements on the court and suppressed their speed. The hand-check had been on its way out since the rule was modified in 1994, but the tactic was killed in order to give way to a faster game and more freedom for guards.
And boy did the guards take advantage.
It is not a coincidence that Duncan's and O'Neal's MVP award were the last one for a traditional back to the basket big man. Since that time, outside of the more unconventional, European style of Kevin Garnett and Dirk Nowitzki, the league's Most Valuable Player award has been given to wing players because the lack of the hand-check allows their skills to be used to its fullest potential.
Steve Nash went from an All-Star point guard at the beginning of the 2000s to a 2x MVP and someone who has reshaped the NBA landscape with the offense he ran with the Phoenix Suns. Watching Stephen Curry playing today is like watching a clone of Nash a decade earlier.
Big men like DeMarcus Cousins and Anthony Davis have struggled to reach the postseason (in Cousins' case, he's never played May basketball) while all the top guards such as Curry, Russell Westbrook, Kyrie Irving, John Wall, Damian Lillard and many more find themselves in May and June basketball all the time. This was the reverse two decades ago. Patrick Ewing and Hakeem Olajuwon were playoff regulars while guards without an inside presence struggled late in the season.
Every major sport goes through phases and rule changes. With the hand-check penalty, we might see the same results as with the restrictions placed on NFL defenses after the 1977 season. The hand-check, as well as the legalization of zone defense at the dawn of the 2000s, changed the NBA forever. We may be seeing the continuation of NBA offenses setting record-breaking numbers and players putting up marks not to be reached until the next generation.