What happens to a player's rating if they suffer a long-term injury?

A player who misses a game for his country is treated exactly the same whatever the reason (injury, poor form etc). In Tests, the player loses 1% of his points for each match missed. In ODIs players lose ½ % of their points for missing a match. Because T20s are more sporadic, players who miss a T20 lose 2% of their points for missing matches.