Jan Siemerink has found clay courts difficult, recording 33–54 across 87 matches (37.9%). The numbers point to a surface that has not consistently suited the game — a key area of opportunity on the calendar. Jan Siemerink has reached 1 final without yet claiming a title on clay — one of the finest margins in tennis.

At Grand Slam level (Roland Garros): Jan Siemerink has struggled at Grand Slam level on clay: 3–9 (25.0%) in 12 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 Siemerink has struggled at Masters level on clay: 10–21 (32.3%) in 31 matches. Improving at this level is the clearest path to a stronger overall record on this surface.

One final reached on clay, without converting it into a title. That final-round experience is valuable groundwork for going one step further next time. 1 semifinal. 5 quarterfinals.

vs. Top 10 on clay: 1–6 (14.3%, 7 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: 5–12 (29.4%); best-of-three: 28–42 (40.0%). 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: 1995 — 8–6 (57.1%) from 14 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.