Fastballs rely on backspin. As discussed, fastballs with higher spin than the MLB average of 2,263.15 seem to "rise", as in they stay up higher than the aforementioned average spin fastballs.

What kind of spin does a fastball have?

Spin Rate is important to a fastball, with fastballs below 1800 rpm and above 2600 rpm being vastly more effective than those that ride the line in the middle. A higher spin rate fastball will appear to rise, and is more difficult to square up.

How many times does a fastball spin?

A four-seam fastball, thrown with backspin, has many RPMs. The average spin rate on a four-seamer in 2020 was 2,306 RPMs. Several Orioles rate above average.