A Pitcher's Stuff
noun
Your sphere might is the force you command over a sphere or ball… in this case, a baseball, making this a pitcher's stuff.
If you're not familiar with this baseball term, we recommend giving it a google. In short, it refers to a pitcher's pitches, judged by how inherently hard those pitches are to hit.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
野球のシーズンが到来する春に近づくにつれて、あの投手の球威は益々増しています。
As we get closer to spring and the arrival of baseball season, that pitcher's stuff has been getting stronger and stronger.