Bill Walsh, head coach of the San Francisco 49ers, wrote down the opening plays of each game in advance. The list grew “from the first five, to first 10, and finally First 15.” According to Lowell Cohn, who wrote a book about Walsh, the reason was “purely diagnostic.” Walsh “would test the defense in various ways.”
The script was not a plan to follow at any cost. Quarterback Steve Young said “it wasn’t a cause for alarm that we didn’t run through the First 15.” NFL teams still script their opening plays. Kansas City Chiefs coordinator Matt Nagy says the script helps them “understand maybe what [the defense is] going to do.”