Solution:
Consider using a conditional count aggregate subquery to return a row number. Below assigns an increasing row number by last name:
SELECT
(SELECT Count(*)
FROM barbara_players t2
WHERE t1.last_name >= t2.last_name) AS player_num,
CONCAT(t1.name,' ', t1.last_name) AS player_name,
t1.date_of_birth, t1.phone, t1.email
FROM barbara_players t1
ORDER BY t1.last_name ASC