The answer is 14.
Based on previous Causeway results, the 10th finisher has consistently had a winning % of 55-57%. Gerry Carter, who finished 10th 2 years ago 16-13 with the same number of players. Translated into 25 games, the minimum is 13.8 wins. Even for last year, it works out roughly to 13.67 - 14/24*30/32 *25
However a lopsided field (low-rated Indian players) may raise the bar required by a bit.
Of course, 14 is not enough for me. Maybe 17 or 18 for a top 5 finish..
And, yes, I know there's a mini 5 days before the big event :) :) :)