Anil Kumble retires : but why?

He could have well been the bowler that he was without being the captain.
I think his career has been shortened because of the captaincy, i.e.
it would have been difficult for him stepping down from the captaincy
and playing like a normal player.

His overall performance isn't too bad if you look at the past few matches.
In 2008, he took 28 wickets in 10 tests. One of the matches against Sri Lanka
had only one innings. So he took 28 out of 190 available wickets.
Which is around 14% of the total possible wickets. It would be even higher
if we consider total number of wickets fallen. So if a bowler is taking around
18-20% of total wickets fallen, and that too when he is not at his peak, what's
wrong?

Kumble is clearly a victim of the unnecessary pressure that has been built
on the senior players by the BCCI-Media nexus. May be Dhoni is a better
captain, but why lose a bowler and one of the best tailend batsmen, for that?