CREATE TABLE table_51857 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

When the home team scored 12.21 (93), what was the average crowd size?
SELECT AVG("Crowd") FROM table_51857 WHERE "Home team score" = '12.21 (93)'
SELECT AVG("Crowd") FROM "table_51857" WHERE "Home team score" = '12.21 (93)'