Robert Rheinberger has found clay courts difficult, recording 4–22 across 26 matches (15.4%). 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): Robert Rheinberger has yet to record a win on clay at this stage — 0–3 across 3 Grand Slam matches. Breaking through here would mark a significant step forward on this surface.

By format on clay — best-of-five: 0–3 (0.0%); best-of-three: 4–19 (17.4%). 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: 1974 — 2–4 (33.3%) from 6 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.