Soriano's Fluky Motion: Illegal?

[Manny A]

Watching Nats games on TV, I've seen a few times when closer Rafael Soriano would take to the mound. And I noticed a very strange pitching motion that I hope I can describe adequately.

With no base runners, when Soriano would engage the plate with his pivot foot, he would bend over while putting his hands together, then stand back up and come to what looks like a Set. While he's coming up to that stand-up position, he would look in and get the signal from his catcher. Almost immediately after he gets set, he takes a step back with his free foot (well, more like stepping towards first base with it) and winds up before delivering his pitch.

Well, at least that's what he used to do. The last game I saw him pitch, however, he stopped the bend-over motion. I'm wondering if he was told he can no longer do that. Anybody have any insight?

Edited to add: I just found a YouTube video of the move, back when he was pitching in pinstripes.

http://www.youtube.com/watch?v=JqVj0QkA3xE

Again, he doesn't do this anymore, at least the last time I saw him work.