Backfield alignments are classified first by how many backs are in the backfield and where they are positioned. Before discussing their positioning it must be determined to what reference they are positioned. We will use the most common conventions for this discussion, starting with the history and evolution of the game as necessary to understand the concepts.
The Flying Vee Era
When the game of football was first being played, the team with the ball would line up in a big vee shaped wedge and run at the defense with the ball carrier protected behind the point of the vee with the two sides angled back to protect his flanks. Then the rules were changed to require seven men on the line of scrimmage and the play to start with the snap of the ball to a player in the backfield with only one player allowed to be in lateral or backwards motion at the the snap.
The Single Wing Era
The game evolved, and soon the way the game was commonly played was from a formation with two ends and four backs: the quarterback, the halfback, the fullback, and the tailback. Some variations moved one of the backs outside the tackle as a wing back, though by that alignment he should be classified as a receiver, since a back would be aligned in the backfield behind the offensive linemen. The ends were usually tight ends in the early evolution of the game, then some teams began occasionally splitting out one or both ends to widen the defense. This was generally done to create more room to run the ball, as at that time the passing game wasn’t very organized in its development. Typically one of the four backs would receive the snap from somewhere sometimes deep in the backfield and they would cross up with each other and one would dive straight ahead with the intention of confusing the defense as to who had the ball and where it was going. Conversely, the two ends would streak down the field and try to catch a pass. Often times the halfback would be the passer. It wasn’t uncommon for the formation to have an unbalanced line. Then along came the wing-T formation.
The Wing-T Era
At some point it became common for the quarterback to move up and take the snap directly from the center. He could then hand the ball off to the fullback or halfback, or fake the handoff and pass the ball to a receiver. The formation now commonly featured a wingback, with one tight end and one split end in varying configurations. Usually the fullback was aligned about three yards behind the quarterback and the half back was aligned even with the fullback behind one of the guards. Sometimes the wing back would come around behind the formation after the snap and take the ball on a reverse.
The Two Wide Receiver Era
Later, it became common to move the wing back player out to a flanker position outside the tight end so the offense would have a wide receiver on each side — a split end and a flanker. Again this further widened the defense. There were still two backs in the backfield (besides the quarterback). Also around this time someone came up with the convention of assigning a letter to each receiver to make play calling easier, using the letters “X”, “Y”, and “Z”. The split end is the “X”, the tight end is the “Y”, and the flanker is the “Z”. It is at this point that we will begin to diverge from the history lesson since many common terminology systems use the tight end as a reference and are based out of a two-back formation.
Closed and Open, Strong and Weak
It used to be that the side the tight end was lined up on was called the “strong” side, with the opposite side called the “weak” side. It is now common to call the side with the tight end the “closed” side, and the opposite side the “open” side. So if the tight end lined up on the right, the right side would be the strong/closed side and the left side would be the weak/open side. If the tight end lined up on the left, the left side would be strong/closed, and the right would be weak/open. Think of it as the open side has an open area between the tackle and the split end for a slot receiver to line up in, whereas on the closed side, that area is closed off. Now lets talk about the backs using the closed and open sides as a reference.
In the Wing-T formation, the fullback usually lined up directly behind the quarterback and wasn’t concerned with where the tight end was for alignment purposes. However, the half back could align even with the fullback either on the closed or open side of the backfield, behind one of the guards. Early on, a color code was used with blue meaning the halfback was aligned to the closed side and brown meaning he was aligned to the open side. A later naming system used the terms near and far, with near meaning to the closed side (near the tight end) and far meaning to the open side.
A later development moved placed a tailback directly behind the fullback. Typically the fullback was in a 3-point or 4-point stance and the tailback was in an even 2-point stance. The fullback would align about three to five yards behind the quarterback with the tailback positioned a couple yards behind the fullback. Often the fullback would lead the tailback through a hole in between the linemen on either side and the tailback would take a handoff from the quarterback hoping to get a block from the fullback.
Bill Walsh later made popular the red alignment, where the backs were split on opposite sides of the backfield with the halfback in a far alignment and the fullback in a near alignment. His splits had the backs aligned a little wider, approximately in the gap between the guard and tackle or on the inside leg of the tackle. He could also tag the formation red right/left “change”, where the the backs would switch positions, with the halfback now near and the fullback far. He didn’t let limit the “change” call to be used just in the red alignment. He expanded the change call to be used in the blue and brown alignments.
Many teams would instruct the halfback when aligning in a blue or brown “change” formation, putting the fullback offset to the side and the halfback behind the quarterback, to align a little deeper depending on the play being called, so that the blocking scheme would have time to develop by the time he got the handoff from the quarterback. Eventually the halfback was essentially aligned much as a tailback would be in the I-Formation with the fullback offset to the closed or open side. These two sets became alternatively known as Blue-I (closed) and Brown-I (open), Strong-I and Weak-I, or Near-I and Far-I.
The Shotgun Formation
At some point it was determined that it would be easier for the quarterback to get back to a position where he could be at a safe distance from the pass rush where he could step up and throw a strong, accurate down field pass if he took the snap from deeper in the backfield. Thus was born the shotgun formation with the quarterback positioned around four or five yards behind the center receiving the snap. With the advent of more pass happy teams using the shotgun snap it was common for one player to move from the backfield to a receiver position. Now with one back in the backfield he was usually aligned in a near or far position, roughly even with the quarterback where he could easily take a handoff or slip out and run a pass route.
The Pistol Formation
Eventually someone figured out the quarterback could take a shotgun snap from a position closer to the center, allowing for the balanced threat of a tailback directly behind the quarterback, and the pistol formation was born. The pistol has the quarterback about three yards behind the center.
Single Back Formations
When there is a single back in the backfield, it has become common for him to align as either a tail back, or in a near or far position. In today’s era of teams using multiple formations and alignments, “tailback” and “halfback” are no longer often considered positions on the depth chart, but instead are one of many positions that a “running back” can align at. This is not the case for the “fullback” position. This term more often is considered a type of player on the roster that is still used primarily as a lead blocker out of the backfield from the “fullback” alignment in the I-Formation or Offset-I. With the proliferation of spread (singleback) offenses, the 2-back set utilizing both a running back and a fullback has declined in use, and with it the fullback position. Some teams don’t even carry a fullback on the roster.
There are other notable backfield alignments that have had periods of great success: the Wishbone, Flexbone, and Power-I. The Wishbone may have predated the I-formation and featured a fullback aligned close behind the quarterback with two halfbacks set one on each side a couple yards behind the fullback. It was a 3-back formation that was used to predominately feature the veer triple option game. The Flexbone is similar with a close fullback, and a slotback on each side of the formation in a close split. Usually just before the snap, one of the slotbacks goes in motion back behind the fullback near where a tailback would align, but with full momentum at the snap. This is technically a single back set motioning to a two back set. It’s also primarily used to run the veer triple option. The Power-I is another 3-back set that features a fullback and tailback in an I-Formation with an additional offset back aligned on either side of the fullback. It is used to get an additional blocker for handoffs to the tailback.