An offensive formation in a football game is how the offense aligns all 11 of its players prior to using a particular play. A team can run or pass out of many formations, but these three backfield formations focus specifically on running backs. Here’s a breakdown of what the three formations look like:
Split-back formation: The runners are aligned behind the two guards about 5 yards behind the line of scrimmage.
Teams use this formation because it’s difficult for the defense to gauge whether the offense is running or passing. With split backs, the backfield is balanced and not aligned toward one side or the other, making it more difficult for the defense to anticipate what the play will be. This formation may be a better passing formation because the backs can swing out of the backfield to either side as receivers.
I formation: The tailback (TB) — the runner who will carry the ball — can place himself as deep as 7 yards from the line of scrimmage.
By stepping this far back, the runner believes he’ll be in full stride when he nears the line of scrimmage. Consequently, the I formation is ideally suited to a team with a great running back. Also, the depth allows him to have complete vision of his blockers and the defensive players’ first reaction to the run. This formation is called the I because the quarterback (QB), fullback (FB), and tailback form an I, with the fullback between the quarterback and tailback.
Offset I formation: The running back (RB) remains deep, 5 to 7 yards from the quarterback. When the running back is this deep, the majority of the time the team plans to run the ball. The fullback (FB) or blocking back can be as close as 3 yards to the line of scrimmage.
The other back wants to be close to his target: the defender he must block. A good fullback needs only 2 yards before making blocking contact. Also, he’s deep enough in case the play requires him to go in motion to either side and swing to the outside for a possible reception. The fullback can be set to the strong side or the weak side of the formation.