Table: afl_2008_debuts
Columns: name
club
debut_round
games_2008
goals_2008
previous_club_s

Question: What is the average number of goals with 21 games for a debut round less than 1?
SQL: SELECT AVG("goals_2008") FROM afl_2008_debuts WHERE "games_2008" = 21 AND "debut_round" < 1