 World: Davis Cup - World Group II - Doubles - Main |
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| | Arevalo M./Miralles L. | Ingildsen J./Nielsen F. | 1:2 (6:2, 4:6, 2:6) | details | 18.09.2022 |
| World: Davis Cup - World Group I - Doubles - Preliminary |
|---|
| | Bopanna R./Sharan D. | Nielsen F./Torpegaard M. | 2:1 (63:7, 6:4, 7:64) | details | 05.03.2022 |
| | Bopanna R./Sharan D. | Ingildsen J./Nielsen F. | CAN. | details | 05.03.2022 |
 Australia: Australian Open - Doubles - Main |
|---|
| 1/16-finals | Daniell M./Nielsen F. | Ram R./Salisbury J. | 0:2 (1:6, 2:6) | details | 22.01.2022 |
| 1/32-finals | Daniell M./Nielsen F. | Karatsev A./Sitak A. | 1:0 RET. (6:2) | details | 20.01.2022 |
| Australia: Adelaide 2 - Doubles - Main |
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| 1/8-finals | Huey T./Nielsen F. | Dodig I./Melo M. | 1:2 (3:6, 6:1, 4:10) | details | 12.01.2022 |
| 1/16-finals | King E./Lawson A. | Huey T./Nielsen F. | 0:2 (62:7, 2:6) | details | 11.01.2022 |
| Australia: Adelaide - Doubles - Main |
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| 1/8-finals | Huey T./Nielsen F. | Brkic T./Gonzalez S. | 1:2 (64:7, 6:4, 8:10) | details | 05.01.2022 |
| 1/16-finals | Lawson A./Vesely J. | Huey T./Nielsen F. | 0:2 (63:7, 2:6) | details | 03.01.2022 |
| World: Davis Cup - World Group II - Doubles - Promotion |
|---|
| | Benchetrit E./Ouahab L. | Nielsen F./Sigsgaard C. | 0:2 (4:6, 4:6) | details | 28.11.2021 |
| | Moundir A./Ouahab L. | Ingildsen J./Nielsen F. | CAN. | details | 28.11.2021 |
 USA: Knoxville - Doubles - Main |
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| 1/8-finals | Blumberg W./Schnur M. | Huey T./Nielsen F. | 2:0 (7:63, 6:2) | details | 10.11.2021 |
| USA: Charlottesville - Doubles - Main |
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| Final | Blumberg W./Schnur M. | Huey T./Nielsen F. | 2:1 (3:6, 6:1, 14:12) | details | 06.11.2021 |
| Semi-finals | Huey T./Nielsen F. | Jung J./Rungkat C. | 2:0 (6:3, 6:3) | details | 05.11.2021 |
| Quarter-finals | Kudla D./Kwiatkowski T. S. | Huey T./Nielsen F. | 0:2 (5:7, 3:6) | details | 05.11.2021 |
| 1/8-finals | Aragone J./Novikov D. | Huey T./Nielsen F. | 0:2 (4:6, 1:6) | details | 03.11.2021 |
 Germany: Ismaning - Doubles - Main |
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| 1/8-finals | Jebavy R./Nielsen F. | Gengel M./Machac T. | 0:2 (2:6, 4:6) | details | 27.10.2021 |
| 1/8-finals | Jebavy R./Nielsen F. | Gojo B./Zuk K. | CAN. | details | 26.10.2021 |
 Belgium: Antwerp - Doubles - Main |
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| 1/8-finals | Nielsen F./Sabanov M. | Molchanov D./Nedovyesov A. | 0:2 (4:6, 4:6) | details | 20.10.2021 |
 France: Orleans - Doubles - Main |
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| Quarter-finals | Huey T./Nielsen F. | Galloway R./Lawson A. | 1:2 (6:3, 5:7, 3:10) | details | 30.09.2021 |
| 1/8-finals | Reese H./Vega Hernandez D. | Huey T./Nielsen F. | 1:2 (6:4, 3:6, 8:10) | details | 28.09.2021 |
 Switzerland: Biel - Doubles - Main |
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| Semi-finals | Huey T./Nielsen F. | Bemelmans R./Masur D. | 0:2 (4:6, 5:7) | details | 24.09.2021 |
| Quarter-finals | Huey T./Nielsen F. | Paul J./Steinegger Y. | 2:1 (6:4, 1:6, 10:4) | details | 23.09.2021 |
| 1/8-finals | Huey T./Nielsen F. | Gengel M./Neuchrist M. | 2:1 (65:7, 6:2, 10:2) | details | 22.09.2021 |
| World: Davis Cup - World Group II - Doubles - Main |
|---|
| | Hannestad B./Nielsen F. | Kovapitukted P./Trongcharoenchaikul W. | 2:0 (6:3, 6:1) | details | 18.09.2021 |
| USA: US Open - Doubles - Main |
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| 1/16-finals | Nielsen F./Pospisil V. | Krawietz K./Tecau H. | 0:2 (612:7, 64:7) | details | 04.09.2021 |
| 1/32-finals | Nielsen F./Pospisil V. | Giron M./Goransson A. | 2:0 (6:3, 7:63) | details | 03.09.2021 |
| USA: Atlanta - Doubles - Main |
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| 1/8-finals | Goransson A./Nielsen F. | Popyrin A./Reid M. | 1:2 (64:7, 6:2, 9:11) | details | 28.07.2021 |
| Switzerland: Gstaad - Doubles - Main |
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| 1/8-finals | Bergs Z./Griekspoor T. | Goransson A./Nielsen F. | 2:0 (6:3, 6:4) | details | 21.07.2021 |
| 1/8-finals | Hanfmann Y./Polmans M. | Goransson A./Nielsen F. | CAN. | details | 20.07.2021 |
 Sweden: Bastad - Doubles - Main |
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| Quarter-finals | Arends S./Pel D. | Goransson A./Nielsen F. | 2:0 (6:2, 6:2) | details | 15.07.2021 |
| 1/8-finals | Bagnis F./Coria F. | Goransson A./Nielsen F. | 0:2 (4:6, 3:6) | details | 14.07.2021 |
 United Kingdom: Wimbledon - Doubles - Main |
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| 1/32-finals | Nielsen F./Skugor F. | Kubot L./Melo M. | CAN. | details | 30.06.2021 |
| United Kingdom: Eastbourne - Doubles - Main |
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| 1/8-finals | Nielsen F./Skugor F. | Ram R./Salisbury J. | 0:2 (5:7, 3:6) | details | 23.06.2021 |
| Germany: Halle - Doubles - Main |
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| 1/16-finals | Saville L./Thompson J. | Nielsen F./Skugor F. | 2:0 (6:3, 6:4) | details | 15.06.2021 |
| Germany: Stuttgart - Doubles - Main |
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| 1/8-finals | Nielsen F./Rojer J. | Daniell M./Oswald P. | 1:2 (5:7, 7:610, 4:10) | details | 10.06.2021 |
| France: French Open - Doubles - Main |
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| 1/32-finals | Molteni A./Nielsen F. | Dodig I./Polasek F. | 1:2 (5:7, 7:66, 66:7) | details | 01.06.2021 |
 Serbia: Belgrade 2 - Doubles - Main |
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| 1/8-finals | Erlich J./Vasilevski A. | Molteni A./Nielsen F. | 2:1 (6:4, 4:6, 10:3) | details | 24.05.2021 |
| France: Lyon - Doubles - Main |
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| 1/8-finals | Molteni A./Nielsen F. | Kontinen H./Roger-Vasselin E. | 0:2 (2:6, 64:7) | details | 17.05.2021 |
 Portugal: Estoril - Doubles - Main |
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| 1/8-finals | Molteni A./Nielsen F. | Behar A./Escobar G. | 0:2 (1:6, 4:6) | details | 28.04.2021 |
| Serbia: Belgrade - Doubles - Main |
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| 1/8-finals | Berrettini M./Vavassori A. | Molteni A./Nielsen F. | 2:0 (7:67, 6:4) | details | 20.04.2021 |
 Italy: Cagliari - Doubles - Main |
|---|
| Quarter-finals | Berrettini J./Berrettini M. | Huey T./Nielsen F. | 2:0 (7:65, 6:3) | details | 08.04.2021 |
| 1/8-finals | Huey T./Nielsen F. | Ebden M./Sharan D. | 2:0 (6:1, 6:4) | details | 07.04.2021 |
 Qatar: Doha - Doubles - Main |
|---|
| Quarter-finals | Cabal J. S./Farah R. | Nielsen F./Puetz T. | 1:0 RET. (6:3, 0:0) | details | 10.03.2021 |
| 1/8-finals | Basilashvili N./Bublik A. | Nielsen F./Puetz T. | 0:2 (1:6, 2:6) | details | 09.03.2021 |
 Netherlands: Rotterdam - Doubles - Qualification |
|---|
| Semi-finals | Nielsen F./Puetz T. | Arends S./Pel D. | 0:2 (3:6, 4:6) | details | 27.02.2021 |
| France: Montpellier - Doubles - Main |
|---|
| 1/8-finals | Nielsen F./Puetz T. | Jebavy R./Vesely J. | 1:2 (4:6, 6:3, 5:10) | details | 24.02.2021 |
| Australia: Australian Open - Doubles - Main |
|---|
| 1/32-finals | Duckworth J./Polmans M. | Cacic N./Nielsen F. | 2:0 (6:4, 6:4) | details | 11.02.2021 |
| Australia: Melbourne (Murray River Open) - Doubles - Main |
|---|
| 1/16-finals | Bopanna R./Nielsen F. | Duckworth J./Polmans M. | 0:2 (4:6, 3:6) | details | 02.02.2021 |
