A lot can change on cricket tours. Tarun Nethula went away to the West Indies and India as the future of New Zealand spin bowling; a 29-year-old leg-break bowler with a national contract who might pressure Daniel Vettori in the latter part of his career.
Nethula returned home having lost his cricketing mojo; a bowler bereft of guile and confidence who was struggling to land, let alone spin the ball.
There is no single reason for his demise.
Leg spin bowling is arguably the most difficult art of the game to master. So much can go right when the ball pitches and rips the rough on a good length; far more can go wrong in the process getting there.
Shane Warne is a perfect case study. Midway through his third test in Sri Lanka he had one wicket and his average was 335. Then, with Sri Lanka needing 31 runs to win chasing 181, Warne took three wickets in 13 balls without conceding a run to mop up the innings and the match. His career rarely dipped again.