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defense / match coverage
Four deep defenders match vertical releases by quarter while safeties read inside receivers for pass or run.
Animated assignment view
Corners and safeties hold balanced depth while underneath defenders align to reroute number two receivers.
Ball at the line
How it works
Corners control outside verticals and safeties match inside verticals, with underneath defenders rerouting routes into those matchups. Safeties can trigger downhill when their key blocks instead of releasing.
Deny vertical routes without abandoning safety involvement in the run fit.
Four defenders each protect a deep quarter, but they turn that zone into man-like coverage when a receiver runs vertically through it.
Quarters is a family of match rules; communication on switch releases determines whether its four-deep appearance remains structurally sound.
Call structure
The two-high shell resembles Cover 2 or Cover 6 until the corners and safeties execute vertical match rules.
{
"schema": "openplay-football",
"schemaVersion": "0.1",
"id": "cover-4-quarters",
"slug": "cover-4-quarters",
"name": "Cover 4 Quarters",
"side": "defense",
"category": "match-coverage",
"personnel": {
"id": "nickel-personnel",
"name": "Nickel",
"grouping": "4 DL, 2 LB, 3 CB, 2 S",
"positionCounts": {
"DL": 4,
"LB": 2,
"CB": 3,
"S": 2
}
},
"formation": {
"id": "even-front",
"name": "Even Front",
"family": "four-down",
"strength": "balanced",
"description": "An even front supports a balanced four-deep secondary shell with safeties reading inside releases."
},
"situationTags": [
"two-high",
"match-coverage",
"long-yardage"
],
"players": [
{
"id": "le",
"position": "DE",
"label": "E",
"initialCoordinate": {
"x": 20,
"y": 1
},
"alignment": "Left edge",
"side": "defense",
"ratingRole": "passRush"
},
{
"id": "dt",
"position": "DT",
"label": "T",
"initialCoordinate": {
"x": 24,
"y": 1
},
"alignment": "Left tackle",
"side": "defense",
"ratingRole": "passRush"
},
{
"id": "nt",
"position": "DT",
"label": "N",
"initialCoordinate": {
"x": 29,
"y": 1
},
"alignment": "Right tackle",
"side": "defense",
"ratingRole": "runDefense"
},
{
"id": "re",
"position": "DE",
"label": "E",
"initialCoordinate": {
"x": 33,
"y": 1
},
"alignment": "Right edge",
"side": "defense",
"ratingRole": "passRush"
},
{
"id": "will",
"position": "LB",
"label": "W",
"initialCoordinate": {
"x": 22,
"y": 6
},
"alignment": "Weak hook",
"side": "defense",
"ratingRole": "zoneCoverage"
},
{
"id": "mike",
"position": "LB",
"label": "M",
"initialCoordinate": {
"x": 31,
"y": 6
},
"alignment": "Strong hook",
"side": "defense",
"ratingRole": "zoneCoverage"
},
{
"id": "lcb",
"position": "CB",
"label": "C",
"initialCoordinate": {
"x": 6,
"y": 7
},
"alignment": "Left quarter",
"side": "defense",
"ratingRole": "zoneCoverage"
},
{
"id": "nickel",
"position": "CB",
"label": "N",
"initialCoordinate": {
"x": 17,
"y": 5
},
"alignment": "Apex left",
"side": "defense",
"ratingRole": "zoneCoverage"
},
{
"id": "rcb",
"position": "CB",
"label": "C",
"initialCoordinate": {
"x": 48,
"y": 7
},
"alignment": "Right quarter",
"side": "defense",
"ratingRole": "zoneCoverage"
},
{
"id": "ls",
"position": "S",
"label": "S",
"initialCoordinate": {
"x": 18,
"y": 13
},
"alignment": "Left quarter",
"side": "defense",
"ratingRole": "zoneCoverage"
},
{
"id": "rs",
"position": "S",
"label": "S",
"initialCoordinate": {
"x": 36,
"y": 13
},
"alignment": "Right quarter",
"side": "defense",
"ratingRole": "zoneCoverage"
}
],
"preSnap": {
"description": "Corners and safeties hold balanced depth while underneath defenders align to reroute number two receivers.",
"shifts": []
},
"assignments": [
{
"id": "left-outside-quarter",
"playerId": "lcb",
"type": "zone-coverage",
"zone": [
{
"x": 0,
"y": 8
},
{
"x": 14,
"y": 8
},
{
"x": 14,
"y": 35
},
{
"x": 0,
"y": 35
}
],
"responsibility": "Match the widest vertical release in the left outside quarter."
},
{
"id": "left-inside-quarter",
"playerId": "ls",
"type": "zone-coverage",
"zone": [
{
"x": 10,
"y": 9
},
{
"x": 27,
"y": 9
},
{
"x": 27,
"y": 35
},
{
"x": 10,
"y": 35
}
],
"responsibility": "Match the left inside vertical and support the run when number two blocks."
},
{
"id": "right-inside-quarter",
"playerId": "rs",
"type": "zone-coverage",
"zone": [
{
"x": 27,
"y": 9
},
{
"x": 44,
"y": 9
},
{
"x": 44,
"y": 35
},
{
"x": 27,
"y": 35
}
],
"responsibility": "Match the right inside vertical and support the run when number two blocks."
},
{
"id": "right-outside-quarter",
"playerId": "rcb",
"type": "zone-coverage",
"zone": [
{
"x": 40,
"y": 8
},
{
"x": 53,
"y": 8
},
{
"x": 53,
"y": 35
},
{
"x": 40,
"y": 35
}
],
"responsibility": "Match the widest vertical release in the right outside quarter."
},
{
"id": "will-under",
"playerId": "will",
"type": "zone-coverage",
"zone": [
{
"x": 10,
"y": 2
},
{
"x": 27,
"y": 2
},
{
"x": 27,
"y": 13
},
{
"x": 10,
"y": 13
}
],
"responsibility": "Wall inside routes and carry crossers to help."
},
{
"id": "mike-under",
"playerId": "mike",
"type": "zone-coverage",
"zone": [
{
"x": 27,
"y": 2
},
{
"x": 44,
"y": 2
},
{
"x": 44,
"y": 13
},
{
"x": 27,
"y": 13
}
],
"responsibility": "Wall inside routes and carry crossers to help."
},
{
"id": "left-rush",
"playerId": "le",
"type": "pass-rush",
"path": [
{
"type": "straight",
"to": {
"x": 23,
"y": -7
}
}
],
"technique": "Contain"
},
{
"id": "inside-rush",
"playerId": "dt",
"type": "pass-rush",
"path": [
{
"type": "straight",
"to": {
"x": 26,
"y": -6
}
}
],
"technique": "B-gap"
},
{
"id": "nose-rush",
"playerId": "nt",
"type": "pass-rush",
"path": [
{
"type": "straight",
"to": {
"x": 28,
"y": -6
}
}
],
"technique": "A-gap"
},
{
"id": "right-rush",
"playerId": "re",
"type": "pass-rush",
"path": [
{
"type": "straight",
"to": {
"x": 31,
"y": -7
}
}
],
"technique": "Contain"
}
],
"timeline": [
{
"type": "pre-snap",
"atMs": 0
},
{
"type": "snap",
"atMs": 500
},
{
"type": "assignment-start",
"atMs": 550,
"playerId": "ls"
},
{
"type": "play-end",
"atMs": 4500
}
],
"narrative": {
"summary": "Four deep defenders match vertical releases by quarter while safeties read inside receivers for pass or run.",
"fullExplanation": "Corners control outside verticals and safeties match inside verticals, with underneath defenders rerouting routes into those matchups. Safeties can trigger downhill when their key blocks instead of releasing.",
"strategicPurpose": "Deny vertical routes without abandoning safety involvement in the run fit.",
"idealSituations": [
"Third and long",
"Against four vertical threats",
"When offenses use run-pass conflicts"
],
"strengths": [
"Four vertical matchups",
"Safeties can fit the run",
"Balanced leverage"
],
"weaknesses": [
"Shallow crossers stretch underneath defenders",
"Play action can hold safeties",
"Post-wheel combinations stress rules"
],
"keyRead": "Safeties read number two: carry vertical, pass off shallow movement, or trigger when he blocks.",
"watchFor": [
"Safeties matching seams",
"Corners staying above outside routes",
"Underneath defenders rerouting crossers"
],
"beginnerExplanation": "Four defenders each protect a deep quarter, but they turn that zone into man-like coverage when a receiver runs vertically through it.",
"advancedNote": "Quarters is a family of match rules; communication on switch releases determines whether its four-deep appearance remains structurally sound."
},
"simulation": {
"difficulty": "advanced",
"conceptTags": [
"match-coverage",
"quarters",
"two-high"
],
"baseSuccessRate": 0.62,
"yardRange": {
"min": -8,
"max": 38
},
"turnoverRisk": 0.038
},
"defensiveStructure": {
"front": "Even four-down front",
"personnel": "Nickel 4-2-5",
"coverage": "Cover 4 Quarters",
"rushPlan": "Rush four with balanced edges while seven defenders pattern-match the release distribution.",
"runFits": [
"Safeties key number two for run-pass",
"Linebackers fit interior gaps",
"Corners provide late force support",
"Ends set hard edges"
],
"disguise": "The two-high shell resembles Cover 2 or Cover 6 until the corners and safeties execute vertical match rules.",
"strengths": [
"Vertical route control",
"Balanced run-pass answers",
"Split-field flexibility"
],
"weaknesses": [
"Shallow crossers",
"Play-action cross",
"Complex switch releases"
],
"idealSituations": [
"Third and long",
"Four-receiver formations",
"Explosive-pass tendency"
],
"vulnerableConcepts": [
"mesh",
"play-action-cross",
"halfback-screen"
]
}
}