Carlos Castellan has found clay courts difficult, recording 25–42 across 67 matches (37.3%). 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): Carlos Castellan is 2–2 (50.0%) across 4 Grand Slam matches — below .500, though the elite draw depth at the Slams makes that a notoriously difficult barrier to crack.

5 quarterfinals on clay, including one run to the semifinal — regularly reaching that stage is a solid baseline, with the next step being to break through to the final rounds more often.

vs. Top 10 on clay: 0–4 (0.0%, 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: 2–2 (50.0%); best-of-three: 23–40 (36.5%). Significantly better in five-set matches — a strong physical profile on clay that tends to tell as matches and tournaments progress.

Best season: 1981 — 7–9 (43.8%) from 16 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.