Task: Text to Code
Input (English): Step 1: For each row in players table, find the corresponding rows in matches table.
Step 2: find each value of first_name in the results of step 1 along with the average winner_rank of the corresponding rows to each value
Output (English): SELECT Avg ( T2.winner_rank ) , T1.first_name FROM players AS T1 JOIN matches AS T2 ON T1.player_id = T2.loser_id GROUP BY T1.first_name