Stefan Kozlov has found hard courts difficult, recording 4–17 across 21 matches (19.0%). The numbers point to a surface that has not consistently suited the game — a key area of opportunity on the calendar.

At Grand Slam level (Australian Open & US Open): 1–2 across just 3 matches — still very early days at this level on hard.

vs. Top 10 on hard: 0–3 (0.0%, 3 matches). Top 10 opponents have represented a clear ceiling on hard; addressing that deficit is the single biggest lever for improving the overall record here.

By format on hard — best-of-five: 1–2 (33.3%); best-of-three: 3–15 (16.7%). Significantly better in five-set matches — a strong physical profile on hard that tends to tell as matches and tournaments progress.

Best season: 2022 — 4–6 (40.0%) from 10 matches. The best single-season display to date — a useful reference point as the hard record continues to develop.