The postseason has arrived for college softball with the start of the NCAA Softball Tournament regional round — the first step on the Road to the Women's College World Series in Oklahoma City, Oklahoma.

Former Oklahoma pitcher Jordy Bahl played a crucial role in the Sooners' run to the 2023 WCWS, leading the Sooners to a three-peat and reminding softball fans of the importance of elite pitching. While in baseball a pitching staff can be leaned on, softball can come down to just one pitcher potentially carrying her team to a big run in the tournament.

REQUIRED READING: NCAA Softball Tournament bracket: Schedule, TV channels, streaming, scores for Road to WCWS

The pitching rules of softball are a major reason why the game is played differently than baseball, and why one pitcher can carry an entire team. Despite softball moving toward more of a committee approach in recent years, the roster size difference between the two sports also makes it harder to depend on more arms.

Here's what you need to know about the difference between pitching in college softball and college baseball, as well as why softball pitchers throw underhand:

Why do college softball pitchers throw underhand?

A regulation softball is roughly 12 inches in circumference and weighs between 6.7-7.3 ounces. Conversely, a regulation baseball measures 9 inches in circumference, weighs a more uniform 5 ounces. The size difference makes it easier to throw a softball with velocity underhand versus how it would come out being thrown overhand.

There are no set rules for baseball pitchers having to throw the ball overhand, which is why sometimes pitchers can throw at different angles, including sidearm pitchers and submarine (underhand) pitchers. However, in softball, it is a rule to throw the ball underhand.

Rule 10 of the NCAA rulebook goes into great detail on the mechanics of a legal pitch — which include pitching position, taking the signal, start of the pitch, windup, step/stride and delivery. That said, the crux is that the ball must be delivered underhand, with the release of the ball occurring below the hip.

Per Rule 10.6:

• 10.6.1: Once the hands have separated and the pitching arm begins the clockwise motion that will result in the release of the pitch, not more than 1 1/2 revolutions of the pitching arm may occur.

• 10.6.2: The pitcher’s step/stride to the batter must be continuous.

• 10.6.3: The pitch shall be released underhand and the hand shall travel below the hip.

• 10.6.4: The release of the pitch and follow-through of the hand and wrist must be forward.

• 10.6.5: The pitcher may not make another arm revolution after releasing the ball.

Softball pitching velocity vs. baseball pitching velocity

Fans may look at softball games and see much slower velocity from pitchers and assume that there's a major difference in how hard pitches are thrown. But it's a good thing to remember that the distance from the softball circle is 43 feet to home plate, while the distance from the pitcher's mound is 60 feet. Baseball mounds are also 18 feet in diameter in height, while softball pitchers deliver from flat ground.

According to TopVelocity.net, a softball pitch coming in at 70 miles per hour is equivalent to a 101.2 MPH pitch in baseball, when factoring in distance and how the ball is thrown. A batter has about 0.360 seconds to react to a pitch coming in at that velocity. Even a 63 MPH pitch in softball clocks in at 91.1 MPH equivalent in baseball, giving hitters a 0.400 reaction time.

What is a riseball?

A common myth: A riseball is not a high fastball, a common pitch in baseball.

The riseball is a fast pitch in softball, like a fastball, but has a late break and rise in trajectory, causing it to rise as the batter swings — often resulting in a miss. Like a high fastball in two-strike counts, the riseball is used similarly to induce strikeouts.

Riseballs are high-velocity pitches, which are normally clocked between 60 to 75 mph in collegiate softball. The most dominant pitchers are capable of speed in excess of 70 MPH. Here's an example of a riseball from Bahl against Texas, when she was a freshman.

Is throwing underhand safer than throwing overhand?

With more velocity than ever in baseball, the cases of Tommy John surgery have gone up in recent years. However, that has not been the case in softball. But that doesn't mean throwing a softball has less wear and tear, despite softball pitching aces throwing more innings than their baseball counterparts.

Matthew Smith, assistant professor of orthopedic surgery at Washington University in St. Louis, conducted a 2018 study on pitchers' fatigue in softball compared to baseball, recruiting 100 14-18-year-old players competing in two- or three-day tournaments.

“The dogma involving throwing athletes is that the underhand pitch is thought to be safer, but there have been biomechanical studies in recent years indicating that the stresses on the shoulder are very similar, regardless of whether one is pitching overhand or underhand,” Smith said. “The idea that we should protect these softball pitchers hasn’t really caught on.

“Because there aren’t as many pitchers on most softball teams as there are on baseball teams, coaches tend to ‘ride’ the ones who are successful. Most don’t realize they’re putting the pitcher at risk, but it turns out that the windmill style of pitching that girls use isn’t as safe as some might think.”

This article originally appeared on Oklahoman: Why do college softball pitchers throw underhand? 2024 NCAA Softball Tournament pitching rules