to time to confuse the defense or force them to devote more attention to possible pass catchers. Specific offensive strategies Using a combination of passing plays and running plays, the offense tries to gain the yards needed for a first down, touchdown, or field goal. Over the years several football coaches and offensive coordinators have developed some well-known and widely used offensive strategies: Option offense Run and shoot offense Smashmouth offense Air Coryell Spread offense West Coast offense Pistol offense Pro-style offense Marty ball Air Raid offense Play calling systems Distinct from the offensive strategies or philosophies, which govern how a team moves the ball down the field, whether a team relies on downfield passes, short passes, inside runs, etc. are the ways in which plays are called. These play calling systems often developed alongside certain offensive strategies, though the systems themselves can work with any strategy. The differences between the systems focus on the specific language used to communicate plays to players. In the NFL, three basic systems predominate: The West Coast system, which developed alongside the West Coast offense, uses specific words to describe formations, blocking schemes, and the routes that runners or pass receivers run. A typical play name would read "FB West Right Slot 372 Y Stick": FB West Right Slot describes the formation, 372 describes the blocking scheme, while Y Stick describes the route run by the primary receiver (Y receiver or tight end). The Coryell system, which developed alongside the Air Coryell offense, is based on a numerical code known as a "route tree". Play calling uses a three digit number, for example 896, where each digit tells a specific receiver which route to run: The leftmost receiver runs an "8" or post route, the middle receiver runs a "9" or go route, and the rightmost receiver runs a "6" or in route. The Erhardt–Perkins system, developed in the 1970s by two assistant coaches with the New England Patriots, is based on single word concepts rather than assigning each player a role in the play. One word, say "ghost", tells each receiver what to do; the concept is divorced from the formation, so regardless of the formation, each player, based on where he is lined up, runs the proper pattern determined by the "ghost" concept. This places a heavy emphasis on memorization (as every player needs to know every route in every concept, not