Jade Dernbach was picked for this limited over series against Sri Lanka after coming on leaps and bounds for Surrey over the past couple of years. A skiddy-ish swing bowler who can move it either way, much of Jade's trumpeting has been due to his slower ball. Coming from the back of the hand, it reduces Jade's regular high 80's to a deceptive low 60 mph, and has been a big part of getting him a lot of county wickets over the past couple of years, which has been instrumental in his rise to the full England squad.
But Dernbach is using it far too often. It's clear he knows just what a good slower ball he has, and is deploying it far more readily than he should. Whether it's a question of him not having the experience to know exactly when it should come or whether it's him showing the selectors that he has a good slower ball is beside the point. In his first six international balls he bowled three slower balls, and has been going at that sort of rate ever since. The Sri Lankan batsmen, knowing a slower ball is likely almost every ball, are hanging back in their creases and waiting for it - massively negating any effect that the slower ball could have.
It's been long complained that England don't have enough One Day variation, and Jade's slower ball can be exactly that. However, it will only be effective if used properly. An "X Factor" ball should not be the stock ball - it should be used as a surprise tactic. Batsmen should always have the possibility of a slower ball in the back of their minds, but it should only be used when they've been lulled into a false sense of security after being worn down by 'regular' bowling. At the moment, the Sri Lankan batsmen are readying themselves each ball expecting it to be slower, which means that when it inevitably comes every couple of balls, the main bonus of a 'surprise ball' of it being a suprise is lost. Hence Jade not being hugely effective so far in his three international outings.
Jade's slower ball can in time become lethal. But first he should look over to the other dressing room to see how an "X Factor" ball is deployed properly. Malinga's yorkers are world reknowned as the best in the business, and is pretty much a wicket taking ball every time (just like Steven Crook's). But Malinga's effectiveness is enhanced because he doesn't use the yorker every ball (only towards the end of the innings does he revert to the toe-crushers). Batsmen know the ball could come at any time, but unable to confidently predict it, they over-compensate and end up working themselves into a lot of bother. Part of the reason Malinga is so successful is because batsmen ready themselves for a yorker that doesn't come, and are unable to adjust for anything different.
Jade Dernbach is only new to international cricket, and can become an important part of England's ODI attack. However, he first needs to realise that the shock ball isn't much of a shock when he bowls it more often than his stock ball.