# 2021 AFC Champions League knockout stage

The 2021 AFC Champions League knockout stage was played from 13 September to 23 November 2021. A total of 16 teams competed in the knockout stage to decide the champions of the 2021 AFC Champions League.

## Qualified teams

The group winners and three best runners-up in the group stage from each region advanced to the round of 16, with both West Region (Groups A–E) and East Region (Groups F–J) having eight qualified teams.
| Region | Group | Winners | Runners-up (best three from each region) |
| West Region | A | Istiklol | Al-Hilal |
| West Region | B | Sharjah | Tractor |
| West Region | C | Esteghlal | — |
| West Region | D | Al-Nassr | — |
| West Region | E | Persepolis | Al-Wahda |
| East Region | F | Ulsan Hyundai | BG Pathum United |
| East Region | G | Nagoya Grampus | Pohang Steelers |
| East Region | H | Jeonbuk Hyundai Motors | — |
| East Region | I | Kawasaki Frontale | Daegu FC |
| East Region | J | Cerezo Osaka | — |

### Combination table

If two group winners played each other, the group winner marked with * hosted the match.
| Qualified | 1A vs | 1B vs | 1C vs | 1D vs | 1E vs |
| 2A/2B/2C | 1B* | 1A | 2A | 2B | 2C |
| 2A/2B/2D | 1D | 2D | 2A | 1A* | 2B |
| 2A/2B/2E | 1E | 2E | 2A | 2B | 1A* |
| 2A/2C/2D | 1C* | 2D | 1A | 2A | 2C |
| 2A/2C/2E | 2C | 2E | 1E* | 2A | 1C |
| 2A/2D/2E | 2D | 2E | 2A | 1E* | 1D |
| 2B/2C/2D | 2D | 1C* | 1B | 2B | 2C |
| 2B/2C/2E | 2C | 1E | 2E | 2B | 1B* |
| 2B/2D/2E | 2D | 1D* | 2E | 1B | 2B |
| 2C/2D/2E | 2D | 2E | 1D* | 1C | 2C |
| Qualified | 1F vs | 1G vs | 1H vs | 1I vs | 1J vs |
| 2F/2G/2H | 1G* | 1F | 2F | 2G | 2H |
| 2F/2G/2I | 1I | 2I | 2F | 1F* | 2G |
| 2F/2G/2J | 1J | 2J | 2F | 2G | 1F* |
| 2F/2H/2I | 1H* | 2I | 1F | 2F | 2H |
| 2F/2H/2J | 2H | 2J | 1J* | 2F | 1H |
| 2F/2I/2J | 2I | 2J | 2F | 1J* | 1I |
| 2G/2H/2I | 2I | 1H* | 1G | 2G | 2H |
| 2G/2H/2J | 2H | 1J | 2J | 2G | 1G* |
| 2G/2I/2J | 2I | 1I* | 2J | 1G | 2G |
| 2H/2I/2J | 2I | 2J | 1I* | 1H | 2H |

## Format

In the knockout stage, the 16 teams played a single-elimination tournament, with the teams split into the two regions until the final. All ties were played as a single-leg match (Regulations Article 9.1). Extra time and penalty shoot-out were used to decide the winners if necessary (Regulations Article 9.3 and 10.1).

## Schedule

The schedule of each round was as follows.
| Round | Date |
| Round of 16 | 13–15 September 2021 |
| Quarter-finals | 16–17 October 2021 |
| Semi-finals | 19–20 October 2021 |
| Final | 23 November 2021 |

## Bracket

The bracket of the knockout stage was determined as follows:
| Round | Format |
| Round of 16 | Matchups within East region and West region decided by a series of permutations, based upon the three best runner-ups who qualified |
| Quarter-finals | Matchups decided by a draw QF West 1 QF West 2 QF East 1 QF East 2 |
| Semi-finals | SF West: Winners of QF West 1 vs. Winners of QF West 2 SF East: Winners of QF East 1 vs. Winners of QF East 2 |
| Final | Winners of SF West vs. Winners of SF East |
| Round of 16 | Round of 16 | Quarter-finals | Quarter-finals | | Semi-finals | Semi-finals | | Final | Final |
| 14 September – Sharjah | 14 September – Sharjah | | | | | | |
| Sharjah | 1 (4) | | | | | | |
| Sharjah | 1 (4) | 16 October – Riyadh (Mrsool) | 16 October – Riyadh (Mrsool) | | | | | |
| Al Wahda (p) | 1 (5) | 16 October – Riyadh (Mrsool) | 16 October – Riyadh (Mrsool) | | | | |
| Al Wahda (p) | 1 (5) | Al Wahda | 1 | | | | |
| 14 September – Al Rayyan (Qatar) | 14 September – Al Rayyan (Qatar) | | Al Wahda | 1 | | | | |
| 14 September – Al Rayyan (Qatar) | 14 September – Al Rayyan (Qatar) | Al-Nassr | 5 | | | | |
| Al Nassr | 1 | Al-Nassr | 5 | | | | |
| Al Nassr | 1 | | | | 19 October – Riyadh (Mrsool) | 19 October – Riyadh (Mrsool) | | |
| Tractor | 0 | | | | 19 October – Riyadh (Mrsool) | 19 October – Riyadh (Mrsool) | |
| Tractor | 0 | | | | Al-Nassr | 1 | |
| 14 September – Dushanbe | 14 September – Dushanbe | | | | | Al-Nassr | 1 | |
| 14 September – Dushanbe | 14 September – Dushanbe | | | | Al-Hilal | 2 | |
| Istiklol | 0 | | | | Al-Hilal | 2 | |
| Istiklol | 0 | 16 October – Riyadh (Prince) | 16 October – Riyadh (Prince) | | | | | |
| Persepolis | 1 | 16 October – Riyadh (Prince) | 16 October – Riyadh (Prince) | | | | |
| Persepolis | 1 | Persepolis | 0 | | | | |
| 13 September – Dubai (UAE) | 13 September – Dubai (UAE) | | Persepolis | 0 | | | | |
| 13 September – Dubai (UAE) | 13 September – Dubai (UAE) | Al-Hilal | 3 | | | | |
| Esteghlal | 0 | Al-Hilal | 3 | | | | |
| Esteghlal | 0 | | | | | | | 23 November – Riyadh (King) | 23 November – Riyadh (King) |
| Al-Hilal | 2 | | | | | | | 23 November – Riyadh (King) | 23 November – Riyadh (King) |
| Al-Hilal | 2 | | | | | | | Al-Hilal | 2 |
| 15 September – Jeonju | 15 September – Jeonju | | | | | | | | Al-Hilal | 2 |
| 15 September – Jeonju | 15 September – Jeonju | | | | | | | Pohang Steelers | 0 |
| Jeonbuk Hyundai Motors (p) | 1 (4) | | | | | | | Pohang Steelers | 0 |
| Jeonbuk Hyundai Motors (p) | 1 (4) | 17 October – Jeonju | 17 October – Jeonju | | | | | | |
| BG Pathum United | 1 (2) | 17 October – Jeonju | 17 October – Jeonju | | | | | | |
| BG Pathum United | 1 (2) | Jeonbuk Hyundai Motors | 2 | | | | | | |
| 14 September – Ulsan | 14 September – Ulsan | | Jeonbuk Hyundai Motors | 2 | | | | | | |
| 14 September – Ulsan | 14 September – Ulsan | Ulsan Hyundai (a.e.t.) | 3 | | | | | | |
| Ulsan Hyundai (p) | 0 (3) | Ulsan Hyundai (a.e.t.) | 3 | | | | | | |
| Ulsan Hyundai (p) | 0 (3) | | | | 20 October – Jeonju | 20 October – Jeonju | | | | |
| Kawasaki Frontale | 0 (2) | | | | 20 October – Jeonju | 20 October – Jeonju | | | |
| Kawasaki Frontale | 0 (2) | | | | Ulsan Hyundai | 1 (4) | | | |
| 15 September – Osaka | 15 September – Osaka | | | | | Ulsan Hyundai | 1 (4) | | | |
| 15 September – Osaka | 15 September – Osaka | | | | Pohang Steelers (p) | 1 (5) | |
| Cerezo Osaka | 0 | | | | Pohang Steelers (p) | 1 (5) | |
| Cerezo Osaka | 0 | 17 October – Jeonju | 17 October – Jeonju | | | | | |
| Pohang Steelers | 1 | 17 October – Jeonju | 17 October – Jeonju | | | | |
| Pohang Steelers | 1 | Pohang Steelers | 3 | | | | |
| 14 September – Toyota | 14 September – Toyota | | Pohang Steelers | 3 | | | | |
| 14 September – Toyota | 14 September – Toyota | Nagoya Grampus | 0 | | | | |
| Nagoya Grampus | 4 | Nagoya Grampus | 0 | | | | |
| Daegu FC | 2 | | | | | | |

## Round of 16
### Summary

The round of 16 was played over one leg, with the matchups determined by the combination tables based on which group runners-up qualified.
West Region :
| Team 1 | Score | Team 2 |
East Region :
| Team 1 | Score | Team 2 |

### East Region
## Quarter-finals
### Summary

The quarter-finals were played over one leg, with the matchups and home team decided by draw held on 17 September at 15:00 (UTC+8) in Kuala Lumpur, Malaysia.
West Region :
| Team 1 | Score | Team 2 |
East Region :
| Team 1 | Score | Team 2 |

### East Region
## Semi-finals
### Summary

The semi-finals were played over one leg.
West Region :
| Team 1 | Score | Team 2 |
East Region :
| Team 1 | Score | Team 2 |

### East Region
## Final

The final was played over a single leg on 23 November. The host was determined on a rotational basis, with the match hosted by team from the West Region in odd-numbered years (Regulations 9.1.2).