CREATE TABLE table_6387 ("Rank" FLOAT, "Name" TEXT, "Attempts" FLOAT, "Net Yds" FLOAT, "Yds/Att" FLOAT, "Touchdowns" FLOAT, "Long" FLOAT, "Start" FLOAT)

What is the average net yds for the player who had a long of 68 and started after 1984?
SELECT AVG("Net Yds") FROM table_6387 WHERE "Long" = '68' AND "Start" > '1984'
SELECT AVG("Net Yds") FROM "table_6387" WHERE "Long" = '68' AND "Start" > '1984'