 Spain: Madrid - Singles - Main |
|---|
| 1/32-finals | Paul T. | Klein L. | 2:1 (65:7, 6:1, 6:4) | details | 26.04.2024 |
| 1/64-finals | Klein L. | Llamas Ruiz P. | 2:1 (6:1, 4:6, 7:64) | details | 24.04.2024 |
| Spain: Madrid - Singles - Qualification |
|---|
| Final | Tirante T. A. | Klein L. | 0:2 (3:6, 3:6) | details | 23.04.2024 |
| Semi-finals | Martin Tiffon P. | Klein L. | 0:2 (3:6, 2:6) | details | 22.04.2024 |
 Croatia: Split - Singles - Main |
|---|
| 1/16-finals | Klein L. | Moeller E. | 0:2 (63:7, 3:6) | details | 09.04.2024 |
 Portugal: Estoril - Singles - Qualification |
|---|
| Final | Klein L. | Faria J. | 1:2 (4:6, 7:63, 1:6) | details | 31.03.2024 |
| Semi-finals | Klein L. | Araujo P. | 2:0 (6:3, 6:0) | details | 30.03.2024 |
 USA: Miami - Singles - Main |
|---|
| 1/64-finals | Michelsen A. | Klein L. | 2:0 (7:65, 6:2) | details | 21.03.2024 |
| USA: Miami - Singles - Qualification |
|---|
| Final | Mensik J. | Klein L. | 0:2 (66:7, 5:7) | details | 19.03.2024 |
| Semi-finals | Klein L. | Paire B. | 2:0 (6:1, 7:62) | details | 18.03.2024 |
| USA: Indian Wells - Singles - Main |
|---|
| 1/32-finals | Ruud C. | Klein L. | 2:0 (6:4, 7:64) | details | 10.03.2024 |
| 1/64-finals | Moreno De Alboran N. | Klein L. | 0:2 (68:7, 4:6) | details | 09.03.2024 |
| USA: Indian Wells - Singles - Qualification |
|---|
| Final | Klein L. | Svajda Z. | 2:1 (6:4, 66:7, 6:3) | details | 05.03.2024 |
| Semi-finals | Marterer M. | Klein L. | 0:2 (2:6, 4:6) | details | 04.03.2024 |
 Qatar: Doha - Singles - Qualification |
|---|
| Final | Muller A. | Klein L. | 2:0 (6:4, 6:4) | details | 18.02.2024 |
| Semi-finals | Zhukayev B. | Klein L. | 0:2 (4:6, 3:6) | details | 17.02.2024 |
 Bahrain: Manama - Singles - Main |
|---|
| 1/16-finals | Klein L. | Trungelliti M. | 1:2 (4:6, 6:3, 3:6) | details | 13.02.2024 |
 World: Davis Cup - World Group - Singles - Qualification |
|---|
| | Lajovic D. | Klein L. | CAN. | details | 03.02.2024 |
| | Kecmanovic M. | Klein L. | 0:2 (62:7, 2:6) | details | 02.02.2024 |
 Australia: Australian Open - Singles - Main |
|---|
| 1/32-finals | Zverev A. | Klein L. | 3:2 (7:5, 3:6, 4:6, 7:65, 7:67) | details | 18.01.2024 |
| 1/64-finals | Kwon S. | Klein L. | 1:3 (60:7, 6:4, 63:7, 3:6) | details | 16.01.2024 |
| Australia: Australian Open - Singles - Qualification |
|---|
| Final | Klein L. | Napolitano S. | 2:0 (7:62, 7:63) | details | 12.01.2024 |
| Semi-finals | Kudla D. | Klein L. | 1:2 (3:6, 7:62, 4:6) | details | 11.01.2024 |
| Quarter-finals | Trungelliti M. | Klein L. | 1:2 (3:6, 6:3, 3:6) | details | 09.01.2024 |
| Australia: Brisbane - Singles - Main |
|---|
| 1/8-finals | Arnaldi M. | Klein L. | 2:1 (6:4, 3:6, 7:5) | details | 03.01.2024 |
| 1/16-finals | Klein L. | Baez S. | 2:1 (4:6, 6:3, 6:4) | details | 02.01.2024 |
| Australia: Brisbane - Singles - Qualification |
|---|
| Final | Klein L. | Cressy M. | 2:1 (4:6, 7:68, 6:4) | details | 31.12.2023 |
| Semi-finals | Halys Q. | Klein L. | 0:2 (4:6, 61:7) | details | 30.12.2023 |
 Germany: Ismaning - Singles - Main |
|---|
| Semi-finals | Klein L. | Marterer M. | 0:2 (4:6, 4:6) | details | 04.11.2023 |
| Quarter-finals | Klein L. | Rehberg M. H. | 2:0 (6:3, 6:2) | details | 03.11.2023 |
| 1/8-finals | Klein L. | Fatic N. | 2:1 (60:7, 6:4, 6:4) | details | 02.11.2023 |
| 1/16-finals | Dzumhur D. | Klein L. | 1:2 (3:6, 6:3, 1:6) | details | 01.11.2023 |
 Italy: Ortisei - Singles - Main |
|---|
| Final | Klein L. | Kasnikowski M. | 2:1 (64:7, 7:64, 7:66) | details | 29.10.2023 |
| Semi-finals | Klein L. | Harris B. | 2:0 (6:3, 7:65) | details | 28.10.2023 |
| Quarter-finals | Dalla Valle E. | Klein L. | 0:2 (3:6, 2:6) | details | 27.10.2023 |
| 1/8-finals | Klein L. | Basic M. | 2:0 (7:65, 7:63) | details | 26.10.2023 |
| 1/16-finals | Paulson A. | Klein L. | 0:2 (5:7, 4:6) | details | 24.10.2023 |
 Slovakia: Bratislava 2 - Singles - Main |
|---|
| Quarter-finals | Diallo G. | Klein L. | 2:1 (3:6, 7:65, 6:2) | details | 13.10.2023 |
| 1/8-finals | Klein L. | Virtanen O. | 2:0 (6:4, 6:4) | details | 12.10.2023 |
| 1/16-finals | Prizmic D. | Klein L. | 0:2 (0:6, 3:6) | details | 10.10.2023 |
| Spain: Alicante - Singles - Main |
|---|
| 1/8-finals | Klein L. | Marterer M. | 0:2 (3:6, 5:7) | details | 04.10.2023 |
| 1/16-finals | Klein L. | Cox D. | 2:0 (6:3, 6:2) | details | 03.10.2023 |
| 1/16-finals | Klein L. | Ivashka I. | CAN. | details | 03.10.2023 |
 France: St. Tropez - Singles - Main |
|---|
| 1/8-finals | Klein L. | Broady L. | 0:2 (2:6, 2:6) | details | 22.09.2023 |
| 1/16-finals | Klein L. | Marie J. | 2:1 (4:6, 6:3, 6:3) | details | 19.09.2023 |
| World: Davis Cup - World Group I - Singles - Main |
|---|
| | Skorilas A. | Klein L. | CAN. | details | 17.09.2023 |