Igor Sijsling has found clay courts difficult, recording 10–23 across 33 matches (30.3%). 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): Igor Sijsling has struggled at Grand Slam level on clay: 2–5 (28.6%) in 7 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): Igor Sijsling is 2–3 (40.0%) across 5 Masters matches — below .500 in the Tour's deepest fields. Lifting that record here would unlock better results across the whole clay swing.

By format on clay — best-of-five: 2–6 (25.0%); best-of-three: 8–17 (32.0%). Slightly stronger in three-set contests on clay, though the five-set record is still respectable.

Best season: 2013 — 4–4 (50.0%) from 8 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.