Wiktionary
new ball
n. 1 (context cricket English) A cricket ball never previously used in a match; a replacement new cricket ball taken by the captain of the bowling side at certain specified times during an innings. 2 (context tennis English) Any of a set of replacement tennis balls issued at specified times in the professional game.
Usage examples of "new ball".
But he was alive, still mobile, and in the trees, and from here on in it was a whole new ball game-But he had dropped the gun.
He is always inventing a new ball, and it is a safe four to the batsman every time.
But on Martin's desk in the real room, what looked like a new ball had appeared.
Sharpe heard the screams of the marksmen in her rigging, watched them fall, then rammed a new ball down his musket.