What's the loss of the game with the opponent of the Nationals with a score of 7-1?
CREATE TABLE "game_log" (
  "date" text,
  "opponent" text,
  "score" text,
  "loss" text,
  "attendance" real,
  "record" text
);
SELECT "loss" FROM "game_log" WHERE "opponent"='nationals' AND "score"='7-1';