Per Hjertquist has found clay courts difficult, recording 30–42 across 72 matches (41.7%). 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): Per Hjertquist is 4–4 (50.0%) across 8 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 — 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: 0–10 (0.0%, 10 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: 5–6 (45.5%); best-of-three: 25–36 (41.0%). Slightly better in five-set matches on clay — a positive sign for the Slams specifically.

Best season: 1979 — 6–4 (60.0%) from 10 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.