Why don't they use it? Is it hard for them to execute it as a second serve consistently? Or is it not safe as the kick? This is the one I'm talking about: http://www.youtube.com/watch?v=mM1P2ej4YtY&feature=related I heard once that they don't use it because "it get's too predictable and it is easy to return it". Well, I think that's pure nonsense because if that were true then the kick serve which just goes straight and up would be even worse of a choice than the twist which changes direction in the air and when it lands. Others have said that they hit them all the time, but I've never seen a serve just like the one Federer hit there been used "all the time" by anyone. I've seen many second serves that curve a lot in the air, or that bounce really high, but I've never seen one that changes that much direction wehn landing as that one.