Accidental Sidespin from a backhand stroke

G'day Alois and Jeff, 

I'm trying to help a fellow player improve their backhand, they seem to be improving but every couple of strokes put sidespin onto the ball. When asked about it they tell me it's accidental. What could be the cause of this and how can we/I help to improve the technique of this guy? 

Regards Jake

Hi Jake,

Get him to focus on the flight of the ball to start with.  Get him to recognise when the ball is curving and going straight.

Then get him to feel his hand position when he is doing these two variations.  Hopefully he will start to see the link between the two.  It will tend to be get sidespin when he is dropping his wrist.