They will be out there throughout the baseball playoffs, on the pitching mound each day, though they will not be easy to see. They range from seven to nine centimeters in length. Some are thick, others thin and faded. They tell the story of the modern pitcher.
About a quarter of active major league pitchers have had elbow surgery to repair a damaged ulnar collateral ligament. Some have had it multiple times. The operation, known as Tommy John surgery, after the first pitcher to undergo it, leaves players with a crescent-shaped scar inside the elbow.
The scar is the physical mark of both the epidemic and an individual player's history. Each scar, like rings on a stump, reveals the past: which doctor performed the operation, how long ago the player had it and whether he had it more than once.
"The funny thing is," said David Altchek, the Mets' doctor, "nobody ever sees it except the batter."
The scar, of course, depends partly on the surgeon. Even two members of the same pitching rotation, of about the same age, can have very different scars. The Mets' two aces, Matt Harvey and Jacob deGrom, were operated on by different surgeons who used different techniques.