 USA: Pittsburgh - Singles - Main |
|---|
| 1/16-finals | Hernandez A. | Callahan H. | 2:0 (6:2, 6:2) | details | 27.06.2018 |
| USA: Waco - Singles - Main |
|---|
| 1/8-finals | Callahan H. | Shane R. | 0:2 (63:7, 2:6) | details | 29.11.2017 |
| 1/16-finals | Butler S. | Callahan H. | 0:2 (4:6, 4:6) | details | 28.11.2017 |
| USA: Columbus - Singles - Main |
|---|
| 1/8-finals | Callahan H. | Sarkissian A. | 0:2 (2:6, 5:7) | details | 23.11.2017 |
| 1/16-finals | Vaghela V. | Callahan H. | 0:2 (4:6, 3:6) | details | 21.11.2017 |
| USA: Laguna Niguel - Singles - Main |
|---|
| Quarter-finals | Callahan H. | Craig H. | 1:2 (3:6, 6:1, 3:6) | details | 22.09.2017 |
| 1/8-finals | Callahan H. | Bullard J. | 0:0 RET. (4:0) | details | 21.09.2017 |
| 1/16-finals | Descotte M. F. | Callahan H. | 0:2 (3:6, 4:6) | details | 19.09.2017 |
| USA: Claremont - Singles - Main |
|---|
| 1/16-finals | Verboven L. | Callahan H. | 2:1 (7:68, 4:6, 6:4) | details | 13.09.2017 |
| USA: Edwardsville - Singles - Main |
|---|
| Semi-finals | Ram Harel O. | Callahan H. | 2:1 (6:3, 1:6, 6:3) | details | 12.08.2017 |
| Quarter-finals | Perez A. | Callahan H. | 1:2 (6:3, 1:6, 4:6) | details | 11.08.2017 |
| 1/8-finals | Callahan H. | Rybakov A. | 2:0 (7:5, 7:5) | details | 10.08.2017 |
| 1/16-finals | Callahan H. | Johnson E. J. | 2:0 (6:4, 6:2) | details | 08.08.2017 |
| USA: Decatur - Singles - Main |
|---|
| 1/8-finals | Dougaz A. | Callahan H. | 2:0 (6:4, 6:4) | details | 03.08.2017 |
| 1/16-finals | Nguyen D. | Callahan H. | 1:2 (6:4, 1:6, 64:7) | details | 02.08.2017 |
| USA: Champaign 2 - Singles - Main |
|---|
| 1/16-finals | Riffice S. | Callahan H. | 2:0 (7:5, 6:3) | details | 24.07.2017 |
| USA: Champaign - Singles - Main |
|---|
| 1/16-finals | Adams H. | Callahan H. | 2:1 (6:3, 5:7, 6:3) | details | 18.07.2017 |
| USA: Pittsburgh - Singles - Main |
|---|
| 1/8-finals | Callahan H. | Lama G. | 1:2 (6:4, 63:7, 4:6) | details | 29.06.2017 |
| 1/16-finals | Kirchheimer S. | Callahan H. | 0:2 (3:6, 1:6) | details | 28.06.2017 |
| USA: Rochester - Singles - Main |
|---|
| 1/16-finals | Lama G. | Callahan H. | 2:1 (6:4, 0:6, 7:65) | details | 20.06.2017 |
| USA: Buffalo - Singles - Main |
|---|
| 1/8-finals | Callahan H. | Uchida K. | 0:2 (3:6, 4:6) | details | 15.06.2017 |
| 1/16-finals | Callahan H. | Gozun A. | 2:0 (6:1, 7:64) | details | 14.06.2017 |
| USA: Orlando 2 - Singles - Main |
|---|
| 1/16-finals | Ramanathan R. | Callahan H. | 2:0 (6:1, 6:2) | details | 01.03.2017 |
| USA: Indian Harbour Beach - Singles - Main |
|---|
| 1/16-finals | Kypson P. | Callahan H. | 2:1 (3:6, 6:4, 6:2) | details | 23.02.2017 |
| USA: Weston - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Vasilyev I. | 1:2 (2:6, 6:0, 4:6) | details | 25.01.2017 |
| USA: Columbus 2 - Singles - Main |
|---|
| 1/16-finals | Krueger M. | Callahan H. | 2:0 (6:4, 6:3) | details | 22.11.2016 |
 United Kingdom: Barnstaple - Singles - Main |
|---|
| Quarter-finals | Callahan H. | Nielsen F. | 1:2 (6:4, 1:6, 2:6) | details | 11.11.2016 |
| 1/8-finals | Gabb R. | Callahan H. | 1:2 (6:2, 1:6, 4:6) | details | 10.11.2016 |
| 1/16-finals | Bauvy R. | Callahan H. | 0:2 (4:6, 4:6) | details | 09.11.2016 |
| United Kingdom: Sheffield - Singles - Main |
|---|
| 1/8-finals | Patael B. | Callahan H. | 2:0 (6:3, 6:4) | details | 02.11.2016 |
| 1/16-finals | Ridout R. | Callahan H. | 0:2 (4:6, 1:6) | details | 01.11.2016 |
| United Kingdom: Loughborough - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Marti Y. | 0:2 (4:6, 2:6) | details | 26.10.2016 |
| USA: Fountain Valley - Singles - Main |
|---|
| 1/8-finals | Garanganga T. | Callahan H. | 2:1 (6:2, 1:6, 6:4) | details | 29.09.2016 |
| 1/16-finals | Callahan H. | Ejupovic E. | 2:0 (7:5, 6:1) | details | 27.09.2016 |
| USA: Irvine - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Gomez L. | 0:2 (3:6, 65:7) | details | 21.09.2016 |
| USA: Claremont - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Trombetta T. D. | 0:2 (2:6, 4:6) | details | 13.09.2016 |
| USA: Champaign - Singles - Main |
|---|
| 1/16-finals | Polmans M. | Callahan H. | 2:0 (6:3, 6:3) | details | 09.08.2016 |
| USA: Decatur - Singles - Main |
|---|
| 1/16-finals | King E. | Callahan H. | 2:0 (6:3, 7:5) | details | 03.08.2016 |
| USA: Pittsburgh - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Kwiatkowski T. S. | 0:2 (4:6, 1:6) | details | 28.06.2016 |
| USA: Rochester - Singles - Main |
|---|
| 1/8-finals | Pasha N. | Callahan H. | 2:0 (6:3, 7:65) | details | 23.06.2016 |
| 1/16-finals | Carter A. | Callahan H. | 0:2 (2:6, 1:6) | details | 22.06.2016 |
| USA: Buffalo - Singles - Main |
|---|
| 1/8-finals | Gosea F. | Callahan H. | 2:0 (7:64, 7:5) | details | 16.06.2016 |
| 1/16-finals | Callahan H. | Garza D. | 2:0 (7:5, 6:4) | details | 14.06.2016 |
 Italy: Frascati - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Carli C. | 1:2 (4:6, 6:3, 5:7) | details | 18.05.2016 |
| USA: Plantation 2 - Singles - Main |
|---|
| 1/16-finals | Callahan H. | Ore J. A. | 1:2 (6:3, 4:6, 5:7) | details | 17.02.2016 |
| USA: Weston - Singles - Main |
|---|
| 1/16-finals | Spencer W. | Callahan H. | 2:0 (6:0, 6:3) | details | 29.01.2016 |
| USA: Champaign - Singles - Main |
|---|
| 1/16-finals | Ramanathan R. | Callahan H. | 2:1 (4:6, 6:2, 6:1) | details | 12.08.2015 |
| USA: Pittsburgh - Singles - Main |
|---|
| 1/8-finals | Gomez E. | Callahan H. | 2:0 (6:2, 6:3) | details | 02.07.2015 |