Jan Hernych has found clay courts difficult, recording 13–29 across 42 matches (31.0%). 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 (Roland Garros): Jan Hernych has struggled at Grand Slam level on clay: 1–4 (20.0%) in 5 matches. The best-of-five format and elite fields make this the toughest benchmark on this surface.

ATP Masters 1000 on clay (Monte Carlo, Madrid, Rome): Jan Hernych has struggled at Masters level on clay: 1–2 (33.3%) in 3 matches. Improving at this level is the clearest path to a stronger overall record on this surface.

vs. Top 10 on clay: 1–3 (25.0%, 4 matches). Top 10 opponents have represented a clear ceiling on clay; addressing that deficit is the single biggest lever for improving the overall record here.

By format on clay — best-of-five: 1–4 (20.0%); best-of-three: 12–25 (32.4%). Markedly stronger in three-set formats; the win rate drops noticeably in five-setters, which has direct implications for Grand Slam performance on clay.

Best season: 2006 — 4–6 (40.0%) from 10 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.