How many players played as a captain in season year 2008?
played as a captain refers to Role_Desc = 'Captain'; in season year 2008 refers Match_Date like '2008%'
SELECT COUNT(T1.Player_Id) FROM Player_Match AS T1 INNER JOIN Match AS T2 ON T1.Match_Id = T2.Match_Id INNER JOIN Rolee AS T3 ON T1.Role_Id = T3.Role_Id WHERE T3.Role_Desc = 'Captain' AND T2.Match_Date LIKE '2008%'