EAST RUTHERFORD, N.J. — When Eli Manning drops back to throw his first pass Sunday against the Dallas Cowboys, the football in his hands will be as familiar as an old friend.

That is because the ball has been scoured, scrubbed, soaked and seasoned, a breaking-in process that takes months and ensures that every ball used by the Giants in a game will meet Manning’s exact preferences. The leather will have been softened, the grip enhanced and the overall feel painstakingly assessed.

There are no new balls thrown around in an N.F.L. game. A new ball, despised for its sheen and waxy gloss, is as popular as a late hit.

For every N.F.L. game, each team has 12 to 20 balls that it has meticulously groomed and prepared according to the needs of its starting quarterback. The balls, brushed and primed using various obvious and semisecret techniques, bear the team logo and are switched out from sideline to sideline depending on which team is on offense.