Job hazards, or, "Tennis, anyone?"

Working in lawn care has its hazards. Yesterday I was trimming in an overgrown back yard and someone (my husband, Dave) was using the ZTR riding mower.
All of a sudden I felt something slam into my left breast. I doubled over and nearly got the wind knocked out of me as I gasped from surprise and a sharp pain. Dave's open chute lawn mower had propelled a tennis ball 20 feet before I stopped it with my mammary gland.
You can see the mark it left on my grimy t-shirt, right on the "ice" in "Service," which is what I needed to put on it once I got home. I am waiting for a purple bruise (but don't wait for THOSE photos, sorry).
I see that Serena Williams can serve a tennis ball at 130 mph on a good day. I am wondering how fast the ZTR mower served it to me. Surely people have inadvertently gotten in the way of a serve before. I guess I need to toughen up.