CREATE TABLE "singles_27_15_12" (
  "outcome" text,
  "date" text,
  "surface" text,
  "opponent" text,
  "score" text
);

Question: What suface during the game that had Yevgeny Kafelnikov as an opponent?
SQL: SELECT "surface" FROM "singles_27_15_12" WHERE "opponent"='yevgeny kafelnikov';