The doosra costs a bowler the one thing that made him dangerous

Turning the ball the other way needs a flatter, faster arm action, and flight is usually the price of admission.

Every young off spinner wants the one that goes the other way, and most of them get worse the season they learn it.

Look at the wrist. A conventional off break is delivered with the fingers dragging down the seam and the wrist behind the ball, which lets the bowler loop it, drop it, hold it back in the air. Flight is not decoration. It is the entire trap: the ball is above the batter's eyeline longer, he commits early, and the drift and dip do the work before the pitch is even involved. The doosra needs the wrist turned in and under, closer to a leg spinner's position but with the fingers still on top, and that action almost forces a flatter, quicker trajectory. You cannot loop it easily. So the bowler stops looping anything, because he does not want two visibly different actions.

That is the trade nobody explains to a nineteen-year-old. He gains a delivery that beats the outside edge maybe twice a match and he loses the dip that got him wickets every match.

There is also the elbow question, which I think has been discussed dishonestly for twenty years. The fifteen degree extension tolerance exists because human elbows hyperextend and nobody bowls with a perfectly rigid arm. Fine. But this particular delivery is very hard to bowl legally at pace with a genuine off spinner's grip, and the sport's response has been to test bowlers in laboratories, clear them, and then watch them get reported again. We have chosen an enforcement circus over an honest answer about whether the ball is compatible with the law.

The good news is that the best finger spinners of the last decade largely stopped caring. They went back to flight, added a ball that goes straight on with the arm, and built their reputations on changes of pace and angle rather than a mystery ball. The undercutter, the arm ball, the one released from wide of the crease. Those are all legal, all repeatable, and none of them require you to be filmed in a motion capture suit.

If you want to be watched, bowl the doosra. If you want to take wickets in your thirties, learn to hold one back.