Defending Trips Into (FIB/FSL)

How to handle three WRs to the short side of the field.

One question I get regularly is how do I handle Trips into the boundary (FIB)? On the surface, putting three players into the boundary is counterintuitive to what Spread offenses are trying to do. Space is relative and leverage is a premium. Placing the three WRs into the boundary can force a defense to overreact to the skill and leave the field wide open.

**Coaches Note: There are several ways to ID the passing strenght into the boundary. I use the accromy FIB, or Formation Into the Boundary. Another popular one is FSL, or Formation to Sideline. Either works, but wanted to give context.

In many cases, Trips FIB sets are used when the offense is trying to gain leverage on the defense. Naturally, the three WRs create a “Bunch” set. A Bunch refers to the three WRs bunched together in a cluster. When playing man teams, these formations can be used to rub defenders off their defenders to create space. To the field side, if a defense overleverages the field Safety or overrotates to the Trips, the offense can now cut off the edge players and create massive amounts of space for the offense to work into the field (think Outside Zone or Stretch to the field).

Finally, by placing all the WRs in a constrained space the offense is isolating the field CB. Depending on the arm strength of the QB and ability of the “X” WR, the offense can now run deep shots or Slants back into space. This is why it is important to have a plan on defense in regards to Trips into the boundary (3x1 FIB).

To combat the massive amounts of space, the defense needs to build walls to the field through the front and secondary alignments. In a four-down defense, this can be as simple as placing the 3 and 5 techniques away from the Trips set. For three-down defenses, the front can be set to where the field overhang is a box or force player who will force everything back to the short side (above).

In a two-high system, the Field Safety will align on or near the hash at his normal depth. I refer to this as “Hash Control.” These alignments leverage the space the offense has and builds natural walls.

Coverage wise, the Trips create a Bunch formation that needs to be dealt with similarly to how the defense would react to a bunch set to the field. Most offenses will not run a three vertical scheme out of the boundary. There is just not enough space. Most route combinations into the boundary are rub routes, Hi-Lo concepts, and screens. This uses the constrained space to their advantage by getting WRs moving in different directions, forcing the defense to divvy them out properly.

To leverage the alignment from depth, a defense needs to stay in a two-high scheme. A DC can choose to play Cover 3 to this formation. If doing so, Cover 6 or a weak rotation would be preferred so you can leverage the Slant of “X” and keep an overhang to the field (I would do this from a two-high presentation).

To the Trips, my favorite way to attack FIB is with my base 3x1 coverage, Stress. When placed into the boundary, Stress essentially plays like BOX or basic Quarters. The defense should play the law of averages and assume that the offense is not trying to go three vertical. Even if they do, the Ni will take all of #2, which is usually a Switch Vertical or “rub” Wheel in the case of Vertical routes.

Related Content: Defending Trips with STRESS

This “box” distribution allows the CB and Safety to play “rail” techniques. In a true Zone-Quarters system, the CB and Safety play the numbers and hash respectively. This allows them to stay at home against Deep Cross (Post/Corner) or any other route combination that sends two guys deep to only switch them later on. The Ni will push anything flat or trigger on any screen while the Mike (or Will) holds the Seam/Curl, collecting any Under route headed back to the field (and now we have created a BOX!).


Film Study

In the first clip, the offense is going to run what I call “A-Pick.” This is a popular play in 7-on-7, but some teams will run it during the regular season. This play is really good if the defense doesn’t have an overhang to the field side (ex. - kicks to the boundary Trips). By placing all three WRs into the boundary and the RB to the field, the offense is trying to outrun any box defender and iso-block the overhang.

Below, the ILB to the RB does a good job of pushing with the RB. Like you would want versus an actual Iso, the defense has an inside and outside shoulder player on the block. To the boundary, the offense runs a Deep Switch that is easily picked up by the Stress/Box scheme. The OLB does an excellent job of sitting underneath the Comeback and the Safety (who is “railing” the hash) easily collects the Post coming back to the field.


In clip #2, the same opponent chooses to use a sideline vertical stretch to attack the Stress call. The CB easily anticipates and carries the vertical of #1. With a double push outside by #2 and #3, the Safety hinges open to #1 anticipating a Post by either vertical WR. In this offensive concept, the #2 WR is running a “follow” route and will sit down at the sticks. Had the WR broke inside, the Safety would have easily collected him.

Underneath, the OLB pushes with the flat attacking route. One coaching point here is to tell the OLB to “COF” (cough) the bait route (Flat). COF stands for: Curl Over Flat. Hold the Curl and let the ball bring you down. At the last second, the OLB hinges open and plays the mid-point. The QB throws the ball and it is tipped for an interception by the CB. Even versus a Sideline Flood, Stress gets defenders at each level.


One vertical “Shot” route that teams like to use into the boundary is the Deep Switch concept (Post/Corner or “Scissors”). Stress, as illustrated, acts as a natural deterrent to this route. When taught right, Stress is like bumpers at the bowling alley and will keep every route condensed inside.

Below, the Safety does a great job of “hash control” and taking the Post. Though he is a little too eager to cut the Corner, a simple speed-turn corrects his coverage. The CB, with eyes inside, picks up the Corner route with ease. The OLB cuts the Flat and takes the “sit down” by #1.


When facing a team that will run Trips into the boundary a defense needs a clear plan on how they are going to attack it. For instance, in 2019 one of our opponents lived in FIB when they ran Trips. This was their base way of running it, rarely running Trips to the field. The condensed space can create issues if a defense approaches Trips FIB the same way they would to the field. Not every coverage works in a tight space.

Stress is a great way to attack the offense into the boundary because it reverts to BOX to most routes and the likelihood of getting three verticals is very low (Stress is good versus that too). One coaching point is to allow the cover down to #3 sit in a 40 (stack the OT). This allows him to be closer to the box yet still close enough to wall the Curl (Snag is not really a great play in limited space).

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The overhang to the boundary can apex #2 and #3 as well. This squeezes the box without giving up anything in coverage. The CB and Safety need to act like bumpers at a bowling alley, stay on the numbers, and hash looking for anything leaking through vertical. Compress the routes and force the QB to throw into a tight window.

Finally, the field has to be leveraged. One major mistake made by DCs is to overreact to Trips and leave the CB isolated or the defense a man short in the fit. The offense is doing this on purpose. The main job of the defense is to constrain space, so when forced with a lot of it, leverage it to the defense’s advantage. This can be done by playing an Under to Trips and setting the 5 tech. wide to box outside runs.

The Field Safety can play near or on the hash, acting as an overhang and walling any in-breaking routes by the “X.” At the least, force the QB to throw outside and deep (which most can’t at the lower levels). My friend Seth Galina (PFF) illustrates my point:

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