At 13 years old should I be throwing a Splitter?

I’m 5" 5’ and 125 lbs. My 4-Seam Fastball is around 65-68 MPH. I’m pretty much a full-time closer on my team. I throw a 4-Seam Fastball, a Side-Arm Cutter (which has the movement of a slider) and just started throwing a splitter about 2 weeks ago. I throw my splitter maybe once or twice each pitching appearance I make. Ever since, I started throwing my Splitter I have had no pain, soreness or discomfort in my arm but I have heard bad things that splitters supposedly do to people’s arms. Should I continue throwing a splitter or discontinue throwing it until im older??? If so, when should I start throwing it again???

I’d be more concerned with your sidearm cutter than your splitter.

Regarding the splitter, I’ve heard people say spreading the fingers wide causes problems but I’ve never seen any concrete evidence of that being true. On the other hand, supinating the hand is accepted by not only pitching experts but also medical experts to be bad. Furthermore, Tom House claims that if you fail to keep your thumb centered under the “V” formed by the two split fingers and, instead, let the thumb creep up the side of the ball toward the index finger, you will have a tendency to supinate. So, throw the splitter but make sure you grip the ball with your thumb centered under the “V”.

As for the sidearm cutter, I think that is a combination that leads to supination which really means you’re no longer throwing a cutter - you’re throwing a slider. You should wait until you’re 17-18 to throw the slider. Or, throw the cutter from a higher arm slot. Of course, if the cutter is the only pitch you throw from th sidearm slot, you’re tipping your pitch.

I used my cutter as a pitch so that batters wouldn’t always be sitting on my fastball and splitter. What pitch should I replace my cutter with??? Also, is my velocity good for a closer at my age level???

If batters are sitting on your fastball, then that tells me you don’t have good enough command of your other pitches to throw them consistently for strike and that the batters have recognized this. The splitter is a good alternative to a change-up but either of these is a good choice for an off-speed pitch. The cutter is also an effective pitch as long as you can hit your spot with it and the batter doesn’t know it’s coming. If you throw it from a higher arm slot (I’m assuming you throw your fastball and splitter from a higher slot), then it should be reasonably safe to throw so keep throwing it. Just make sure you don’t put a big twist into it.

please, for your sake, do not throw a splitter. A splitter should only be used if a curve or slider doesn’t work for you. Also you should not throw breaking stuff till in late highschool/college for longevity.