Softballs in MLB bullpen

I can't speak about the MLB, but I've been using a softball with my youth teams for years. We use them in warm-ups: 1. They are a little heavier than baseballs and 2. After tossing them for a few minutes, the baseball seems like a BB.

We use 'em for curveball spins

Haven't heard of softballs, but I've heard of football throwing before picking up a baseball.

In the off-season and for grip/spin development, the overload (larger-heavier) and the underload (Lighter-Smaller) balls have been used for years in Maryland, and have traveled to the Brewer's farm systems in Phoenix, then Montana, then West Va, than back to Madison, then on to Milwaukee.

The smaller women's softball (ie Dudley XYZ) is a tad smaller than the men's fastpitch softball, which is where many of the Final National Championships are played near and around Oshkosh & Appleton WI.

The smaller 'real' baseballs (Bob Decker makes a product) are great for developing loose wrists while taxing some type of consistent release points for breaking pitches and other off-speed.

We also used softballs to warm up doing long toss. It also got the hand to expand to grip the ball better.

I know that Jose Contreas uses a softball to start to help him with his grip for his forkball. I don't know if it's used for anything else in his case.