Bem, você pode tentar este conjunto de consultas:
(SELECT Name, PositionId, TScore FROM Soccerplayers WHERE PositionID = 1 ORDER BY TScore LIMIT 3)
UNION
(SELECT Name, PositionId, TScore FROM Soccerplayers WHERE PositionID = 2 ORDER BY TScore LIMIT 4)
UNION
(SELECT Name, PositionId, TScore FROM Soccerplayers WHERE PositionID = 3 ORDER BY TScore LIMIT 3)