| 9‑Oct‑2023 | Fairfield CH | Hard | R32 | 220 | 349 | (Alt)Skander Mansouri [TUN] d. Pospisil | 1-6 6-1 6-3 | | 0.58 | 5.7% | 7.1% | 60.0% | 69.0% | 39.3% | 0/4 | 1:18 |
| 2‑Oct‑2023 | Tiburon CH | Hard | R32 | 220 | 199 | Adam Walton [AUS] d. (6)Pospisil | 6-4 7-6(5) | | 0.79 | 6.8% | 5.4% | 47.3% | 71.4% | 48.7% | 4/6 | 1:46 |
| 25‑Sep‑2023 | Charleston CH | Hard | R32 | 186 | 290 | Brandon Holt [USA] d. (3)Pospisil | 6-1 6-3 | | 0.67 | 3.2% | 11.1% | 54.0% | 55.9% | 37.9% | 3/8 | 1:14 |
| 18‑Sep‑2023 | Columbus CH | Hard | QF | 188 | 219 | Ryan Peniston [GBR] d. (4)Pospisil | 7-5 3-6 6-4 | | 0.80 | 6.0% | 3.4% | 51.3% | 73.3% | 49.1% | 12/15 | 3:13 |
| 18‑Sep‑2023 | Columbus CH | Hard | R16 | 188 | 715 | (4)Pospisil d. (WC)James Tracy [USA] | 6-3 6-4 | | 0.78 | 4.3% | 8.7% | 55.4% | 72.5% | 46.3% | 4/4 | 1:53 |
| 18‑Sep‑2023 | Columbus CH | Hard | R32 | 188 | 1107 | (4)Pospisil d. Nishesh Basavareddy [USA] | 7-5 2-6 7-5 | | 1.20 | 14.3% | 2.2% | 61.5% | 75.0% | 54.3% | 5/8 | 2:33 |
| 14‑Sep‑2023 | Davis Cup Finals RR: CAN vs SWE | Hard | RR | 187 | 334 | Pospisil d. Leo Borg [SWE] | 7-6(5) 5-7 6-2 | | 1.44 | 30.1% | 3.6% | 63.9% | 84.9% | 53.3% | 0/2 | |
| 28‑Aug‑2023 | US Open | Hard | Q2 | 192 | 234 | Zachary Svajda [USA] d. Pospisil | 3-6 6-4 6-2 | | 0.86 | 11.4% | 7.6% | 54.4% | 74.4% | 44.4% | 2/5 | 2:10 |
| 28‑Aug‑2023 | US Open | Hard | Q1 | 192 | 132 | Pospisil d. (26)Pedro Martinez [ESP] | 7-6(7) 6-7(3) 6-4 | | 1.01 | 8.7% | 4.7% | 53.5% | 75.0% | 40.7% | 12/16 | 3:29 |
| 7‑Aug‑2023 | Canada Masters | Hard | R64 | 165 | 66 | (Q)Matteo Arnaldi [ITA] d. (WC)Pospisil | 6-4 6-4 | | 0.80 | 11.9% | 15.3% | 37.3% | 72.7% | 45.9% | 4/7 | 1:31 |
| 17‑Jul‑2023 | Granby CH | Hard | R32 | 161 | 244 | Adam Walton [AUS] d. (4)Pospisil | 6-7(7) 7-6(1) 6-1 | | 0.89 | 11.5% | 4.8% | 58.7% | 68.9% | 53.5% | 4/7 | 2:55 |
| 3‑Jul‑2023 | Wimbledon | Grass | Q1 | 157 | 134 | (20)Felipe Meligeni Alves [BRA] d. Pospisil | 6-2 7-6(2) | | 0.80 | 8.3% | 8.3% | 50.0% | 86.7% | 40.0% | 2/4 | 1:23 |
| 13‑Feb‑2023 | Cherbourg CH | Hard | R32 | 111 | 284 | (Alt)Mats Moraing [GER] d. (1)Pospisil | 6-4 7-6(5) | | 0.72 | 11.5% | 2.6% | 47.4% | 75.7% | 39.0% | 5/8 | 1:35 |
| 30‑Jan‑2023 | Koblenz CH | Hard | F | 113 | 100 | (2)Roman Safiullin [RUS] d. (3)Pospisil | 6-2 7-5 | | 0.80 | 7.0% | 5.3% | 59.6% | 67.6% | 39.1% | 1/5 | 1:34 |
| 30‑Jan‑2023 | Koblenz CH | Hard | SF | 113 | 254 | (3)Pospisil d. Zdenek Kolar [CZE] | 6-1 6-3 | | 2.11 | 18.2% | 2.3% | 50.0% | 90.9% | 63.6% | 2/2 | 1:10 |
| 30‑Jan‑2023 | Koblenz CH | Hard | QF | 113 | 306 | (3)Pospisil d. (Alt)Louis Wessels [GER] | 6-4 6-2 | | 1.29 | 17.5% | 3.5% | 45.6% | 84.6% | 48.4% | 1/2 | 1:34 |
| 30‑Jan‑2023 | Koblenz CH | Hard | R16 | 113 | 446 | (3)Pospisil d. (Q)Mats Rosenkranz [GER] | 7-6(6) 7-6(2) | | 1.38 | 17.9% | 4.8% | 53.6% | 77.8% | 61.5% | 5/7 | 2:17 |
| 30‑Jan‑2023 | Koblenz CH | Hard | R32 | 113 | 180 | (3)Pospisil d. Emilio Nava [USA] | 7-5 6-2 | | 1.60 | 10.9% | 3.6% | 65.5% | 86.1% | 42.1% | 1/2 | 1:18 |
| 23‑Jan‑2023 | Quimper CH | Hard | R32 | 99 | 161 | Gijs Brouwer [NED] d. (3)Pospisil | 3-6 6-3 6-3 | | 0.86 | 7.8% | 6.8% | 55.3% | 64.9% | 50.0% | 13/17 | 2:07 |
| 16‑Jan‑2023 | Australian Open | Hard | R128 | 99 | 7 | (6)Felix Auger Aliassime [CAN] d. Pospisil | 1-6 7-6(4) 7-6(3) 6-3 | (ch) | 0.93 | 9.5% | 4.8% | 64.6% | 69.5% | 50.0% | 9/12 | 3:58 |
| 9‑Jan‑2023 | Adelaide 2 | Hard | Q1 | 94 | 84 | (7)Soon Woo Kwon [KOR] d. Pospisil | 6-7(7) 6-3 6-3 | | 0.67 | 14.3% | 3.8% | 52.4% | 72.7% | 54.0% | 3/7 | 2:28 |
| 2‑Jan‑2023 | Adelaide 1 | Hard | Q2 | 98 | 88 | (3)Roman Safiullin [RUS] d. (7)Pospisil | 6-7(5) 6-2 6-3 | | 0.68 | 14.1% | 8.7% | 50.0% | 67.4% | 54.3% | 7/11 | 2:35 |
| 2‑Jan‑2023 | Adelaide 1 | Hard | Q1 | 98 | 147 | (7)Pospisil d. John Millman [AUS] | 7-5 6-2 | | 1.62 | 13.0% | 5.6% | 55.6% | 80.0% | 62.5% | 2/3 | 1:31 |
