The kick serve is venue-dependent and nobody plans for it

The safest second serve in tennis stops being safe the moment the air, the balls or the court stop co-operating.

Every coach teaches the kick serve as the reliable one. Brush up the back of the ball, get topspin and sidespin, clear the net by a good margin, watch it jump away from the returner's backhand. Safe margin, aggressive bounce. It's the closest thing tennis has to a free lunch, and it's the second serve most professionals lean on.

Except the kick serve has a dependency list as long as your arm, and hardly anyone builds a plan around checking it.

It needs air. The jump comes from spin interacting with the atmosphere and then with the court, so at altitude the ball dips less and climbs less off the bounce. It needs a court that grips. On a gritty, high-friction hard court a kicker leaps to shoulder height and the returner is in genuine trouble. On slick, worn grass or a fast low-bouncing indoor surface, the same serve skids and sits at hip height, which is precisely where a returner wants it, and now you've handed over a slow ball in the middle of the box.

It needs the right ball, too. A heavy, fluffy ball gripped hard by the strings takes spin beautifully. A slick new ball on a hot day takes less, and the same swing produces less bite.

So the serve that is safe in one venue is a liability in another, and a player who has only one second serve finds out about it during a match rather than beforehand. That's the problem. Not the technique, the monoculture.

The insurance policy is a slice second serve, and it's undervalued because it looks less impressive. A sliced second wide in the deuce court stays low, moves away from the returner, and works best on exactly the fast, low-bouncing surfaces where the kicker stops kicking. In the ad court it jams into a right-hander's body. It carries less net margin, so it needs to be practised properly rather than improvised at four-all.

The wider point is about preparation. Players scout opponents obsessively and scout venues barely at all, beyond a couple of practice hits. If you know a court is quick and the balls are light, you should walk in knowing your second serve pattern is going to change, the way a golfer knows a links course demands a different ball flight.

One serve for every condition isn't a strength. It's an assumption, and assumptions get broken in the second week.